libphobos/src/std/datetime/date.d

   1 // Written in the D programming language
   2
   3 /++
   4     License:   $(HTTP www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
   5     Authors:   Jonathan M Davis
   6     Source:    $(PHOBOSSRC std/datetime/_date.d)
   7 +/
   8 module std.datetime.date;
   9
  10 import core.time;
  11 import std.traits : isSomeString, Unqual;
  12 import std.typecons : Flag;
  13
  14 version (unittest) import std.exception : assertThrown;
  15
  16
  17 @safe unittest
  18 {
  19     initializeTests();
  20 }
  21
  22
  23 /++
  24     Exception type used by std.datetime. It's an alias to
  25     $(REF TimeException,core,time). Either can be caught without concern about
  26     which module it came from.
  27   +/
  28 alias DateTimeException = TimeException;
  29
  30
  31 /++
  32     Represents the 12 months of the Gregorian year (January is 1).
  33   +/
  34 enum Month : ubyte
  35 {
  36     jan = 1, ///
  37     feb,     ///
  38     mar,     ///
  39     apr,     ///
  40     may,     ///
  41     jun,     ///
  42     jul,     ///
  43     aug,     ///
  44     sep,     ///
  45     oct,     ///
  46     nov,     ///
  47     dec      ///
  48 }
  49
  50
  51 /++
  52     Represents the 7 days of the Gregorian week (Sunday is 0).
  53   +/
  54 enum DayOfWeek : ubyte
  55 {
  56     sun = 0, ///
  57     mon,     ///
  58     tue,     ///
  59     wed,     ///
  60     thu,     ///
  61     fri,     ///
  62     sat      ///
  63 }
  64
  65
  66 /++
  67     In some date calculations, adding months or years can cause the date to fall
  68     on a day of the month which is not valid (e.g. February 29th 2001 or
  69     June 31st 2000). If overflow is allowed (as is the default), then the month
  70     will be incremented accordingly (so, February 29th 2001 would become
  71     March 1st 2001, and June 31st 2000 would become July 1st 2000). If overflow
  72     is not allowed, then the day will be adjusted to the last valid day in that
  73     month (so, February 29th 2001 would become February 28th 2001 and
  74     June 31st 2000 would become June 30th 2000).
  75
  76     AllowDayOverflow only applies to calculations involving months or years.
  77
  78     If set to $(D AllowDayOverflow.no), then day overflow is not allowed.
  79
  80     Otherwise, if set to $(D AllowDayOverflow.yes), then day overflow is
  81     allowed.
  82   +/
  83 alias AllowDayOverflow = Flag!"allowDayOverflow";
  84
  85
  86 /++
  87     Array of the strings representing time units, starting with the smallest
  88     unit and going to the largest. It does not include $(D "nsecs").
  89
  90    Includes $(D "hnsecs") (hecto-nanoseconds (100 ns)),
  91    $(D "usecs") (microseconds), $(D "msecs") (milliseconds), $(D "seconds"),
  92    $(D "minutes"), $(D "hours"), $(D "days"), $(D "weeks"), $(D "months"), and
  93    $(D "years")
  94   +/
  95 immutable string[] timeStrings = ["hnsecs", "usecs", "msecs", "seconds", "minutes",
  96                                   "hours", "days", "weeks", "months", "years"];
  97
  98
  99 /++
 100    Combines the $(REF Date,std,datetime,date) and
 101    $(REF TimeOfDay,std,datetime,date) structs to give an object which holds
 102    both the date and the time. It is optimized for calendar-based operations and
 103    has no concept of time zone. For an object which is optimized for time
 104    operations based on the system time, use $(REF SysTime,std,datetime,systime).
 105    $(REF SysTime,std,datetime,systime) has a concept of time zone and has much
 106    higher precision (hnsecs). $(D DateTime) is intended primarily for
 107    calendar-based uses rather than precise time operations.
 108   +/
 109 struct DateTime
 110 {
 111 public:
 112
 113     /++
 114         Params:
 115             date = The date portion of $(LREF DateTime).
 116             tod  = The time portion of $(LREF DateTime).
 117       +/
 118     this(in Date date, in TimeOfDay tod = TimeOfDay.init) @safe pure nothrow @nogc
 119     {
 120         _date = date;
 121         _tod = tod;
 122     }
 123
 124     @safe unittest
 125     {
 126         {
 127             auto dt = DateTime.init;
 128             assert(dt._date == Date.init);
 129             assert(dt._tod == TimeOfDay.init);
 130         }
 131
 132         {
 133             auto dt = DateTime(Date(1999, 7 ,6));
 134             assert(dt._date == Date(1999, 7, 6));
 135             assert(dt._tod == TimeOfDay.init);
 136         }
 137
 138         {
 139             auto dt = DateTime(Date(1999, 7 ,6), TimeOfDay(12, 30, 33));
 140             assert(dt._date == Date(1999, 7, 6));
 141             assert(dt._tod == TimeOfDay(12, 30, 33));
 142         }
 143     }
 144
 145
 146     /++
 147         Params:
 148             year   = The year portion of the date.
 149             month  = The month portion of the date (January is 1).
 150             day    = The day portion of the date.
 151             hour   = The hour portion of the time;
 152             minute = The minute portion of the time;
 153             second = The second portion of the time;
 154       +/
 155     this(int year, int month, int day, int hour = 0, int minute = 0, int second = 0) @safe pure
 156     {
 157         _date = Date(year, month, day);
 158         _tod = TimeOfDay(hour, minute, second);
 159     }
 160
 161     @safe unittest
 162     {
 163         {
 164             auto dt = DateTime(1999, 7 ,6);
 165             assert(dt._date == Date(1999, 7, 6));
 166             assert(dt._tod == TimeOfDay.init);
 167         }
 168
 169         {
 170             auto dt = DateTime(1999, 7 ,6, 12, 30, 33);
 171             assert(dt._date == Date(1999, 7, 6));
 172             assert(dt._tod == TimeOfDay(12, 30, 33));
 173         }
 174     }
 175
 176
 177     /++
 178         Compares this $(LREF DateTime) with the given $(D DateTime.).
 179
 180         Returns:
 181             $(BOOKTABLE,
 182             $(TR $(TD this &lt; rhs) $(TD &lt; 0))
 183             $(TR $(TD this == rhs) $(TD 0))
 184             $(TR $(TD this &gt; rhs) $(TD &gt; 0))
 185             )
 186      +/
 187     int opCmp(in DateTime rhs) const @safe pure nothrow @nogc
 188     {
 189         immutable dateResult = _date.opCmp(rhs._date);
 190
 191         if (dateResult != 0)
 192             return dateResult;
 193
 194         return _tod.opCmp(rhs._tod);
 195     }
 196
 197     @safe unittest
 198     {
 199         // Test A.D.
 200         assert(DateTime(Date.init, TimeOfDay.init).opCmp(DateTime.init) == 0);
 201
 202         assert(DateTime(Date(1999, 1, 1)).opCmp(DateTime(Date(1999, 1, 1))) == 0);
 203         assert(DateTime(Date(1, 7, 1)).opCmp(DateTime(Date(1, 7, 1))) == 0);
 204         assert(DateTime(Date(1, 1, 6)).opCmp(DateTime(Date(1, 1, 6))) == 0);
 205
 206         assert(DateTime(Date(1999, 7, 1)).opCmp(DateTime(Date(1999, 7, 1))) == 0);
 207         assert(DateTime(Date(1999, 7, 6)).opCmp(DateTime(Date(1999, 7, 6))) == 0);
 208
 209         assert(DateTime(Date(1, 7, 6)).opCmp(DateTime(Date(1, 7, 6))) == 0);
 210
 211         assert(DateTime(Date(1999, 7, 6)).opCmp(DateTime(Date(2000, 7, 6))) < 0);
 212         assert(DateTime(Date(2000, 7, 6)).opCmp(DateTime(Date(1999, 7, 6))) > 0);
 213         assert(DateTime(Date(1999, 7, 6)).opCmp(DateTime(Date(1999, 8, 6))) < 0);
 214         assert(DateTime(Date(1999, 8, 6)).opCmp(DateTime(Date(1999, 7, 6))) > 0);
 215         assert(DateTime(Date(1999, 7, 6)).opCmp(DateTime(Date(1999, 7, 7))) < 0);
 216         assert(DateTime(Date(1999, 7, 7)).opCmp(DateTime(Date(1999, 7, 6))) > 0);
 217
 218         assert(DateTime(Date(1999, 8, 7)).opCmp(DateTime(Date(2000, 7, 6))) < 0);
 219         assert(DateTime(Date(2000, 8, 6)).opCmp(DateTime(Date(1999, 7, 7))) > 0);
 220         assert(DateTime(Date(1999, 7, 7)).opCmp(DateTime(Date(2000, 7, 6))) < 0);
 221         assert(DateTime(Date(2000, 7, 6)).opCmp(DateTime(Date(1999, 7, 7))) > 0);
 222         assert(DateTime(Date(1999, 7, 7)).opCmp(DateTime(Date(1999, 8, 6))) < 0);
 223         assert(DateTime(Date(1999, 8, 6)).opCmp(DateTime(Date(1999, 7, 7))) > 0);
 224
 225
 226         assert(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)).opCmp(
 227                    DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0))) == 0);
 228         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0)).opCmp(
 229                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0))) == 0);
 230         assert(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0)).opCmp(
 231                    DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 0))) == 0);
 232         assert(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33)).opCmp(
 233                    DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))) == 0);
 234
 235         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)).opCmp(
 236                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0))) == 0);
 237         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 238                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) == 0);
 239
 240         assert(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)).opCmp(
 241                    DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33))) == 0);
 242         assert(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33)).opCmp(
 243                    DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33))) == 0);
 244
 245         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 246                    DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))) < 0);
 247         assert(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)).opCmp(
 248                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 249         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 250                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))) < 0);
 251         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)).opCmp(
 252                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 253         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 254                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))) < 0);
 255         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)).opCmp(
 256                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 257
 258         assert(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)).opCmp(
 259                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))) > 0);
 260         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)).opCmp(
 261                    DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))) < 0);
 262         assert(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)).opCmp(
 263                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))) > 0);
 264         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)).opCmp(
 265                    DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))) < 0);
 266
 267         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)).opCmp(
 268                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))) > 0);
 269         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)).opCmp(
 270                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))) < 0);
 271
 272         assert(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)).opCmp(
 273                    DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 274         assert(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 275                    DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))) > 0);
 276         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)).opCmp(
 277                    DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 278         assert(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 279                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))) > 0);
 280         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)).opCmp(
 281                    DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 282         assert(DateTime(Date(2000, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 283                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))) > 0);
 284
 285         assert(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)).opCmp(
 286                    DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))) < 0);
 287         assert(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 288                    DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))) > 0);
 289         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)).opCmp(
 290                    DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))) < 0);
 291         assert(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 292                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33))) > 0);
 293         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)).opCmp(
 294                    DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33))) < 0);
 295         assert(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 296                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))) > 0);
 297
 298         assert(DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)).opCmp(
 299                    DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))) < 0);
 300         assert(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33)).opCmp(
 301                    DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33))) > 0);
 302         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)).opCmp(
 303                    DateTime(Date(1999, 7, 7), TimeOfDay(12, 31, 33))) < 0);
 304         assert(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33)).opCmp(
 305                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 306         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)).opCmp(
 307                    DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33))) < 0);
 308         assert(DateTime(Date(1999, 7, 7), TimeOfDay(12, 30, 33)).opCmp(
 309                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34))) > 0);
 310
 311         // Test B.C.
 312         assert(DateTime(Date(-1, 1, 1), TimeOfDay(12, 30, 33)).opCmp(
 313                    DateTime(Date(-1, 1, 1), TimeOfDay(12, 30, 33))) == 0);
 314         assert(DateTime(Date(-1, 7, 1), TimeOfDay(12, 30, 33)).opCmp(
 315                    DateTime(Date(-1, 7, 1), TimeOfDay(12, 30, 33))) == 0);
 316         assert(DateTime(Date(-1, 1, 6), TimeOfDay(12, 30, 33)).opCmp(
 317                    DateTime(Date(-1, 1, 6), TimeOfDay(12, 30, 33))) == 0);
 318
 319         assert(DateTime(Date(-1999, 7, 1), TimeOfDay(12, 30, 33)).opCmp(
 320                    DateTime(Date(-1999, 7, 1), TimeOfDay(12, 30, 33))) == 0);
 321         assert(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 322                    DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))) == 0);
 323
 324         assert(DateTime(Date(-1, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 325                    DateTime(Date(-1, 7, 6), TimeOfDay(12, 30, 33))) == 0);
 326
 327         assert(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 328                    DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 329         assert(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 330                    DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 331         assert(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 332                    DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))) < 0);
 333         assert(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 334                    DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 335         assert(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 336                    DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))) < 0);
 337         assert(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33)).opCmp(
 338                    DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 339
 340         assert(DateTime(Date(-2000, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 341                    DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))) < 0);
 342         assert(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33)).opCmp(
 343                    DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 344         assert(DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 345                    DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))) < 0);
 346         assert(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33)).opCmp(
 347                    DateTime(Date(-2000, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 348         assert(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33)).opCmp(
 349                    DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))) < 0);
 350         assert(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 351                    DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))) > 0);
 352
 353         // Test Both
 354         assert(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 355                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 356         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 357                    DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 358
 359         assert(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 360                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 361         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 362                    DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33))) > 0);
 363
 364         assert(DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33)).opCmp(
 365                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 366         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 367                    DateTime(Date(-1999, 7, 7), TimeOfDay(12, 30, 33))) > 0);
 368
 369         assert(DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33)).opCmp(
 370                    DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33))) < 0);
 371         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).opCmp(
 372                    DateTime(Date(-1999, 8, 7), TimeOfDay(12, 30, 33))) > 0);
 373
 374         assert(DateTime(Date(-1999, 8, 6), TimeOfDay(12, 30, 33)).opCmp(
 375                    DateTime(Date(1999, 6, 6), TimeOfDay(12, 30, 33))) < 0);
 376         assert(DateTime(Date(1999, 6, 8), TimeOfDay(12, 30, 33)).opCmp(
 377                    DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33))) > 0);
 378
 379         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 33, 30));
 380         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 33, 30));
 381         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 33, 30));
 382         assert(dt.opCmp(dt) == 0);
 383         assert(dt.opCmp(cdt) == 0);
 384         assert(dt.opCmp(idt) == 0);
 385         assert(cdt.opCmp(dt) == 0);
 386         assert(cdt.opCmp(cdt) == 0);
 387         assert(cdt.opCmp(idt) == 0);
 388         assert(idt.opCmp(dt) == 0);
 389         assert(idt.opCmp(cdt) == 0);
 390         assert(idt.opCmp(idt) == 0);
 391     }
 392
 393
 394     /++
 395         The date portion of $(LREF DateTime).
 396       +/
 397     @property Date date() const @safe pure nothrow @nogc
 398     {
 399         return _date;
 400     }
 401
 402     @safe unittest
 403     {
 404         {
 405             auto dt = DateTime.init;
 406             assert(dt.date == Date.init);
 407         }
 408
 409         {
 410             auto dt = DateTime(Date(1999, 7, 6));
 411             assert(dt.date == Date(1999, 7, 6));
 412         }
 413
 414         const cdt = DateTime(1999, 7, 6);
 415         immutable idt = DateTime(1999, 7, 6);
 416         assert(cdt.date == Date(1999, 7, 6));
 417         assert(idt.date == Date(1999, 7, 6));
 418     }
 419
 420
 421     /++
 422         The date portion of $(LREF DateTime).
 423
 424         Params:
 425             date = The Date to set this $(LREF DateTime)'s date portion to.
 426       +/
 427     @property void date(in Date date) @safe pure nothrow @nogc
 428     {
 429         _date = date;
 430     }
 431
 432     @safe unittest
 433     {
 434         auto dt = DateTime.init;
 435         dt.date = Date(1999, 7, 6);
 436         assert(dt._date == Date(1999, 7, 6));
 437         assert(dt._tod == TimeOfDay.init);
 438
 439         const cdt = DateTime(1999, 7, 6);
 440         immutable idt = DateTime(1999, 7, 6);
 441         static assert(!__traits(compiles, cdt.date = Date(2010, 1, 1)));
 442         static assert(!__traits(compiles, idt.date = Date(2010, 1, 1)));
 443     }
 444
 445
 446     /++
 447         The time portion of $(LREF DateTime).
 448       +/
 449     @property TimeOfDay timeOfDay() const @safe pure nothrow @nogc
 450     {
 451         return _tod;
 452     }
 453
 454     @safe unittest
 455     {
 456         {
 457             auto dt = DateTime.init;
 458             assert(dt.timeOfDay == TimeOfDay.init);
 459         }
 460
 461         {
 462             auto dt = DateTime(Date.init, TimeOfDay(12, 30, 33));
 463             assert(dt.timeOfDay == TimeOfDay(12, 30, 33));
 464         }
 465
 466         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 467         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 468         assert(cdt.timeOfDay == TimeOfDay(12, 30, 33));
 469         assert(idt.timeOfDay == TimeOfDay(12, 30, 33));
 470     }
 471
 472
 473     /++
 474         The time portion of $(LREF DateTime).
 475
 476         Params:
 477             tod = The $(REF TimeOfDay,std,datetime,date) to set this
 478                   $(LREF DateTime)'s time portion to.
 479       +/
 480     @property void timeOfDay(in TimeOfDay tod) @safe pure nothrow @nogc
 481     {
 482         _tod = tod;
 483     }
 484
 485     @safe unittest
 486     {
 487         auto dt = DateTime.init;
 488         dt.timeOfDay = TimeOfDay(12, 30, 33);
 489         assert(dt._date == Date.init);
 490         assert(dt._tod == TimeOfDay(12, 30, 33));
 491
 492         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 493         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 494         static assert(!__traits(compiles, cdt.timeOfDay = TimeOfDay(12, 30, 33)));
 495         static assert(!__traits(compiles, idt.timeOfDay = TimeOfDay(12, 30, 33)));
 496     }
 497
 498
 499     /++
 500         Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
 501         are B.C.
 502      +/
 503     @property short year() const @safe pure nothrow @nogc
 504     {
 505         return _date.year;
 506     }
 507
 508     @safe unittest
 509     {
 510         assert(Date.init.year == 1);
 511         assert(Date(1999, 7, 6).year == 1999);
 512         assert(Date(-1999, 7, 6).year == -1999);
 513
 514         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 515         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 516         assert(idt.year == 1999);
 517         assert(idt.year == 1999);
 518     }
 519
 520
 521     /++
 522         Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
 523         are B.C.
 524
 525         Params:
 526             year = The year to set this $(LREF DateTime)'s year to.
 527
 528         Throws:
 529             $(REF DateTimeException,std,datetime,date) if the new year is not
 530             a leap year and if the resulting date would be on February 29th.
 531      +/
 532     @property void year(int year) @safe pure
 533     {
 534         _date.year = year;
 535     }
 536
 537     ///
 538     @safe unittest
 539     {
 540         assert(DateTime(Date(1999, 7, 6), TimeOfDay(9, 7, 5)).year == 1999);
 541         assert(DateTime(Date(2010, 10, 4), TimeOfDay(0, 0, 30)).year == 2010);
 542         assert(DateTime(Date(-7, 4, 5), TimeOfDay(7, 45, 2)).year == -7);
 543     }
 544
 545     @safe unittest
 546     {
 547         static void testDT(DateTime dt, int year, in DateTime expected, size_t line = __LINE__)
 548         {
 549             dt.year = year;
 550             assert(dt == expected);
 551         }
 552
 553         testDT(DateTime(Date(1, 1, 1), TimeOfDay(12, 30, 33)),
 554                1999,
 555                DateTime(Date(1999, 1, 1), TimeOfDay(12, 30, 33)));
 556         testDT(DateTime(Date(1, 1, 1), TimeOfDay(12, 30, 33)),
 557                0,
 558                DateTime(Date(0, 1, 1), TimeOfDay(12, 30, 33)));
 559         testDT(DateTime(Date(1, 1, 1), TimeOfDay(12, 30, 33)),
 560                -1999,
 561                DateTime(Date(-1999, 1, 1), TimeOfDay(12, 30, 33)));
 562
 563         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 564         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 565         static assert(!__traits(compiles, cdt.year = 7));
 566         static assert(!__traits(compiles, idt.year = 7));
 567     }
 568
 569
 570     /++
 571         Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
 572
 573         Throws:
 574             $(REF DateTimeException,std,datetime,date) if $(D isAD) is true.
 575      +/
 576     @property short yearBC() const @safe pure
 577     {
 578         return _date.yearBC;
 579     }
 580
 581     ///
 582     @safe unittest
 583     {
 584         assert(DateTime(Date(0, 1, 1), TimeOfDay(12, 30, 33)).yearBC == 1);
 585         assert(DateTime(Date(-1, 1, 1), TimeOfDay(10, 7, 2)).yearBC == 2);
 586         assert(DateTime(Date(-100, 1, 1), TimeOfDay(4, 59, 0)).yearBC == 101);
 587     }
 588
 589     @safe unittest
 590     {
 591         assertThrown!DateTimeException((in DateTime dt){dt.yearBC;}(DateTime(Date(1, 1, 1))));
 592
 593         auto dt = DateTime(1999, 7, 6, 12, 30, 33);
 594         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 595         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 596         dt.yearBC = 12;
 597         assert(dt.yearBC == 12);
 598         static assert(!__traits(compiles, cdt.yearBC = 12));
 599         static assert(!__traits(compiles, idt.yearBC = 12));
 600     }
 601
 602
 603     /++
 604         Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
 605
 606         Params:
 607             year = The year B.C. to set this $(LREF DateTime)'s year to.
 608
 609         Throws:
 610             $(REF DateTimeException,std,datetime,date) if a non-positive value
 611             is given.
 612      +/
 613     @property void yearBC(int year) @safe pure
 614     {
 615         _date.yearBC = year;
 616     }
 617
 618     ///
 619     @safe unittest
 620     {
 621         auto dt = DateTime(Date(2010, 1, 1), TimeOfDay(7, 30, 0));
 622         dt.yearBC = 1;
 623         assert(dt == DateTime(Date(0, 1, 1), TimeOfDay(7, 30, 0)));
 624
 625         dt.yearBC = 10;
 626         assert(dt == DateTime(Date(-9, 1, 1), TimeOfDay(7, 30, 0)));
 627     }
 628
 629     @safe unittest
 630     {
 631         assertThrown!DateTimeException((DateTime dt){dt.yearBC = -1;}(DateTime(Date(1, 1, 1))));
 632
 633         auto dt = DateTime(1999, 7, 6, 12, 30, 33);
 634         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 635         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 636         dt.yearBC = 12;
 637         assert(dt.yearBC == 12);
 638         static assert(!__traits(compiles, cdt.yearBC = 12));
 639         static assert(!__traits(compiles, idt.yearBC = 12));
 640     }
 641
 642
 643     /++
 644         Month of a Gregorian Year.
 645      +/
 646     @property Month month() const @safe pure nothrow @nogc
 647     {
 648         return _date.month;
 649     }
 650
 651     ///
 652     @safe unittest
 653     {
 654         assert(DateTime(Date(1999, 7, 6), TimeOfDay(9, 7, 5)).month == 7);
 655         assert(DateTime(Date(2010, 10, 4), TimeOfDay(0, 0, 30)).month == 10);
 656         assert(DateTime(Date(-7, 4, 5), TimeOfDay(7, 45, 2)).month == 4);
 657     }
 658
 659     @safe unittest
 660     {
 661         assert(DateTime.init.month == 1);
 662         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)).month == 7);
 663         assert(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)).month == 7);
 664
 665         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 666         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 667         assert(cdt.month == 7);
 668         assert(idt.month == 7);
 669     }
 670
 671
 672     /++
 673         Month of a Gregorian Year.
 674
 675         Params:
 676             month = The month to set this $(LREF DateTime)'s month to.
 677
 678         Throws:
 679             $(REF DateTimeException,std,datetime,date) if the given month is
 680             not a valid month.
 681      +/
 682     @property void month(Month month) @safe pure
 683     {
 684         _date.month = month;
 685     }
 686
 687     @safe unittest
 688     {
 689         static void testDT(DateTime dt, Month month, in DateTime expected = DateTime.init, size_t line = __LINE__)
 690         {
 691             dt.month = month;
 692             assert(expected != DateTime.init);
 693             assert(dt == expected);
 694         }
 695
 696         assertThrown!DateTimeException(testDT(DateTime(Date(1, 1, 1), TimeOfDay(12, 30, 33)), cast(Month) 0));
 697         assertThrown!DateTimeException(testDT(DateTime(Date(1, 1, 1), TimeOfDay(12, 30, 33)), cast(Month) 13));
 698
 699         testDT(DateTime(Date(1, 1, 1), TimeOfDay(12, 30, 33)),
 700                cast(Month) 7,
 701                DateTime(Date(1, 7, 1), TimeOfDay(12, 30, 33)));
 702         testDT(DateTime(Date(-1, 1, 1), TimeOfDay(12, 30, 33)),
 703                cast(Month) 7,
 704                DateTime(Date(-1, 7, 1), TimeOfDay(12, 30, 33)));
 705
 706         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 707         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 708         static assert(!__traits(compiles, cdt.month = 12));
 709         static assert(!__traits(compiles, idt.month = 12));
 710     }
 711
 712
 713     /++
 714         Day of a Gregorian Month.
 715      +/
 716     @property ubyte day() const @safe pure nothrow @nogc
 717     {
 718         return _date.day;
 719     }
 720
 721     ///
 722     @safe unittest
 723     {
 724         assert(DateTime(Date(1999, 7, 6), TimeOfDay(9, 7, 5)).day == 6);
 725         assert(DateTime(Date(2010, 10, 4), TimeOfDay(0, 0, 30)).day == 4);
 726         assert(DateTime(Date(-7, 4, 5), TimeOfDay(7, 45, 2)).day == 5);
 727     }
 728
 729     @safe unittest
 730     {
 731         import std.format : format;
 732         import std.range : chain;
 733
 734         static void test(DateTime dateTime, int expected)
 735         {
 736             assert(dateTime.day == expected, format("Value given: %s", dateTime));
 737         }
 738
 739         foreach (year; chain(testYearsBC, testYearsAD))
 740         {
 741             foreach (md; testMonthDays)
 742             {
 743                 foreach (tod; testTODs)
 744                     test(DateTime(Date(year, md.month, md.day), tod), md.day);
 745             }
 746         }
 747
 748         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 749         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 750         assert(cdt.day == 6);
 751         assert(idt.day == 6);
 752     }
 753
 754
 755     /++
 756         Day of a Gregorian Month.
 757
 758         Params:
 759             day = The day of the month to set this $(LREF DateTime)'s day to.
 760
 761         Throws:
 762             $(REF DateTimeException,std,datetime,date) if the given day is not
 763             a valid day of the current month.
 764      +/
 765     @property void day(int day) @safe pure
 766     {
 767         _date.day = day;
 768     }
 769
 770     @safe unittest
 771     {
 772         import std.exception : assertNotThrown;
 773
 774         static void testDT(DateTime dt, int day)
 775         {
 776             dt.day = day;
 777         }
 778
 779         // Test A.D.
 780         assertThrown!DateTimeException(testDT(DateTime(Date(1, 1, 1)), 0));
 781         assertThrown!DateTimeException(testDT(DateTime(Date(1, 1, 1)), 32));
 782         assertThrown!DateTimeException(testDT(DateTime(Date(1, 2, 1)), 29));
 783         assertThrown!DateTimeException(testDT(DateTime(Date(4, 2, 1)), 30));
 784         assertThrown!DateTimeException(testDT(DateTime(Date(1, 3, 1)), 32));
 785         assertThrown!DateTimeException(testDT(DateTime(Date(1, 4, 1)), 31));
 786         assertThrown!DateTimeException(testDT(DateTime(Date(1, 5, 1)), 32));
 787         assertThrown!DateTimeException(testDT(DateTime(Date(1, 6, 1)), 31));
 788         assertThrown!DateTimeException(testDT(DateTime(Date(1, 7, 1)), 32));
 789         assertThrown!DateTimeException(testDT(DateTime(Date(1, 8, 1)), 32));
 790         assertThrown!DateTimeException(testDT(DateTime(Date(1, 9, 1)), 31));
 791         assertThrown!DateTimeException(testDT(DateTime(Date(1, 10, 1)), 32));
 792         assertThrown!DateTimeException(testDT(DateTime(Date(1, 11, 1)), 31));
 793         assertThrown!DateTimeException(testDT(DateTime(Date(1, 12, 1)), 32));
 794
 795         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 1, 1)), 31));
 796         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 2, 1)), 28));
 797         assertNotThrown!DateTimeException(testDT(DateTime(Date(4, 2, 1)), 29));
 798         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 3, 1)), 31));
 799         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 4, 1)), 30));
 800         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 5, 1)), 31));
 801         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 6, 1)), 30));
 802         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 7, 1)), 31));
 803         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 8, 1)), 31));
 804         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 9, 1)), 30));
 805         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 10, 1)), 31));
 806         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 11, 1)), 30));
 807         assertNotThrown!DateTimeException(testDT(DateTime(Date(1, 12, 1)), 31));
 808
 809         {
 810             auto dt = DateTime(Date(1, 1, 1), TimeOfDay(7, 12, 22));
 811             dt.day = 6;
 812             assert(dt == DateTime(Date(1, 1, 6), TimeOfDay(7, 12, 22)));
 813         }
 814
 815         // Test B.C.
 816         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 1, 1)), 0));
 817         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 1, 1)), 32));
 818         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 2, 1)), 29));
 819         assertThrown!DateTimeException(testDT(DateTime(Date(0, 2, 1)), 30));
 820         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 3, 1)), 32));
 821         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 4, 1)), 31));
 822         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 5, 1)), 32));
 823         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 6, 1)), 31));
 824         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 7, 1)), 32));
 825         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 8, 1)), 32));
 826         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 9, 1)), 31));
 827         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 10, 1)), 32));
 828         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 11, 1)), 31));
 829         assertThrown!DateTimeException(testDT(DateTime(Date(-1, 12, 1)), 32));
 830
 831         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 1, 1)), 31));
 832         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 2, 1)), 28));
 833         assertNotThrown!DateTimeException(testDT(DateTime(Date(0, 2, 1)), 29));
 834         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 3, 1)), 31));
 835         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 4, 1)), 30));
 836         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 5, 1)), 31));
 837         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 6, 1)), 30));
 838         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 7, 1)), 31));
 839         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 8, 1)), 31));
 840         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 9, 1)), 30));
 841         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 10, 1)), 31));
 842         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 11, 1)), 30));
 843         assertNotThrown!DateTimeException(testDT(DateTime(Date(-1, 12, 1)), 31));
 844
 845         auto dt = DateTime(Date(-1, 1, 1), TimeOfDay(7, 12, 22));
 846         dt.day = 6;
 847         assert(dt == DateTime(Date(-1, 1, 6), TimeOfDay(7, 12, 22)));
 848
 849         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 850         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 851         static assert(!__traits(compiles, cdt.day = 27));
 852         static assert(!__traits(compiles, idt.day = 27));
 853     }
 854
 855
 856     /++
 857         Hours past midnight.
 858      +/
 859     @property ubyte hour() const @safe pure nothrow @nogc
 860     {
 861         return _tod.hour;
 862     }
 863
 864     @safe unittest
 865     {
 866         assert(DateTime.init.hour == 0);
 867         assert(DateTime(Date.init, TimeOfDay(12, 0, 0)).hour == 12);
 868
 869         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 870         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 871         assert(cdt.hour == 12);
 872         assert(idt.hour == 12);
 873     }
 874
 875
 876     /++
 877         Hours past midnight.
 878
 879         Params:
 880             hour = The hour of the day to set this $(LREF DateTime)'s hour to.
 881
 882         Throws:
 883             $(REF DateTimeException,std,datetime,date) if the given hour would
 884             result in an invalid $(LREF DateTime).
 885      +/
 886     @property void hour(int hour) @safe pure
 887     {
 888         _tod.hour = hour;
 889     }
 890
 891     @safe unittest
 892     {
 893         assertThrown!DateTimeException((){DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)).hour = 24;}());
 894
 895         auto dt = DateTime.init;
 896         dt.hour = 12;
 897         assert(dt == DateTime(1, 1, 1, 12, 0, 0));
 898
 899         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 900         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 901         static assert(!__traits(compiles, cdt.hour = 27));
 902         static assert(!__traits(compiles, idt.hour = 27));
 903     }
 904
 905
 906     /++
 907         Minutes past the hour.
 908      +/
 909     @property ubyte minute() const @safe pure nothrow @nogc
 910     {
 911         return _tod.minute;
 912     }
 913
 914     @safe unittest
 915     {
 916         assert(DateTime.init.minute == 0);
 917         assert(DateTime(1, 1, 1, 0, 30, 0).minute == 30);
 918
 919         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 920         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 921         assert(cdt.minute == 30);
 922         assert(idt.minute == 30);
 923     }
 924
 925
 926     /++
 927         Minutes past the hour.
 928
 929         Params:
 930             minute = The minute to set this $(LREF DateTime)'s minute to.
 931
 932         Throws:
 933             $(REF DateTimeException,std,datetime,date) if the given minute
 934             would result in an invalid $(LREF DateTime).
 935      +/
 936     @property void minute(int minute) @safe pure
 937     {
 938         _tod.minute = minute;
 939     }
 940
 941     @safe unittest
 942     {
 943         assertThrown!DateTimeException((){DateTime.init.minute = 60;}());
 944
 945         auto dt = DateTime.init;
 946         dt.minute = 30;
 947         assert(dt == DateTime(1, 1, 1, 0, 30, 0));
 948
 949         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 950         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 951         static assert(!__traits(compiles, cdt.minute = 27));
 952         static assert(!__traits(compiles, idt.minute = 27));
 953     }
 954
 955
 956     /++
 957         Seconds past the minute.
 958      +/
 959     @property ubyte second() const @safe pure nothrow @nogc
 960     {
 961         return _tod.second;
 962     }
 963
 964     @safe unittest
 965     {
 966         assert(DateTime.init.second == 0);
 967         assert(DateTime(1, 1, 1, 0, 0, 33).second == 33);
 968
 969         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
 970         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
 971         assert(cdt.second == 33);
 972         assert(idt.second == 33);
 973     }
 974
 975
 976     /++
 977         Seconds past the minute.
 978
 979         Params:
 980             second = The second to set this $(LREF DateTime)'s second to.
 981
 982         Throws:
 983             $(REF DateTimeException,std,datetime,date) if the given seconds
 984             would result in an invalid $(LREF DateTime).
 985      +/
 986     @property void second(int second) @safe pure
 987     {
 988         _tod.second = second;
 989     }
 990
 991     @safe unittest
 992     {
 993         assertThrown!DateTimeException((){DateTime.init.second = 60;}());
 994
 995         auto dt = DateTime.init;
 996         dt.second = 33;
 997         assert(dt == DateTime(1, 1, 1, 0, 0, 33));
 998
 999         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
1000         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
1001         static assert(!__traits(compiles, cdt.second = 27));
1002         static assert(!__traits(compiles, idt.second = 27));
1003     }
1004
1005
1006     /++
1007         Adds the given number of years or months to this $(LREF DateTime). A
1008         negative number will subtract.
1009
1010         Note that if day overflow is allowed, and the date with the adjusted
1011         year/month overflows the number of days in the new month, then the month
1012         will be incremented by one, and the day set to the number of days
1013         overflowed. (e.g. if the day were 31 and the new month were June, then
1014         the month would be incremented to July, and the new day would be 1). If
1015         day overflow is not allowed, then the day will be set to the last valid
1016         day in the month (e.g. June 31st would become June 30th).
1017
1018         Params:
1019             units         = The type of units to add ("years" or "months").
1020             value         = The number of months or years to add to this
1021                             $(LREF DateTime).
1022             allowOverflow = Whether the days should be allowed to overflow,
1023                             causing the month to increment.
1024       +/
1025     ref DateTime add(string units)
1026                     (long value, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) @safe pure nothrow @nogc
1027         if (units == "years" || units == "months")
1028     {
1029         _date.add!units(value, allowOverflow);
1030         return this;
1031     }
1032
1033     ///
1034     @safe unittest
1035     {
1036         auto dt1 = DateTime(2010, 1, 1, 12, 30, 33);
1037         dt1.add!"months"(11);
1038         assert(dt1 == DateTime(2010, 12, 1, 12, 30, 33));
1039
1040         auto dt2 = DateTime(2010, 1, 1, 12, 30, 33);
1041         dt2.add!"months"(-11);
1042         assert(dt2 == DateTime(2009, 2, 1, 12, 30, 33));
1043
1044         auto dt3 = DateTime(2000, 2, 29, 12, 30, 33);
1045         dt3.add!"years"(1);
1046         assert(dt3 == DateTime(2001, 3, 1, 12, 30, 33));
1047
1048         auto dt4 = DateTime(2000, 2, 29, 12, 30, 33);
1049         dt4.add!"years"(1, AllowDayOverflow.no);
1050         assert(dt4 == DateTime(2001, 2, 28, 12, 30, 33));
1051     }
1052
1053     @safe unittest
1054     {
1055         auto dt = DateTime(2000, 1, 31);
1056         dt.add!"years"(7).add!"months"(-4);
1057         assert(dt == DateTime(2006, 10, 1));
1058
1059         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
1060         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
1061         static assert(!__traits(compiles, cdt.add!"years"(4)));
1062         static assert(!__traits(compiles, idt.add!"years"(4)));
1063         static assert(!__traits(compiles, cdt.add!"months"(4)));
1064         static assert(!__traits(compiles, idt.add!"months"(4)));
1065     }
1066
1067
1068     /++
1069         Adds the given number of years or months to this $(LREF DateTime). A
1070         negative number will subtract.
1071
1072         The difference between rolling and adding is that rolling does not
1073         affect larger units. Rolling a $(LREF DateTime) 12 months
1074         gets the exact same $(LREF DateTime). However, the days can still be
1075         affected due to the differing number of days in each month.
1076
1077         Because there are no units larger than years, there is no difference
1078         between adding and rolling years.
1079
1080         Params:
1081             units         = The type of units to add ("years" or "months").
1082             value         = The number of months or years to add to this
1083                             $(LREF DateTime).
1084             allowOverflow = Whether the days should be allowed to overflow,
1085                             causing the month to increment.
1086       +/
1087     ref DateTime roll(string units)
1088                      (long value, AllowDayOverflow allowOverflow = AllowDayOverflow.yes) @safe pure nothrow @nogc
1089         if (units == "years" || units == "months")
1090     {
1091         _date.roll!units(value, allowOverflow);
1092         return this;
1093     }
1094
1095     ///
1096     @safe unittest
1097     {
1098         auto dt1 = DateTime(2010, 1, 1, 12, 33, 33);
1099         dt1.roll!"months"(1);
1100         assert(dt1 == DateTime(2010, 2, 1, 12, 33, 33));
1101
1102         auto dt2 = DateTime(2010, 1, 1, 12, 33, 33);
1103         dt2.roll!"months"(-1);
1104         assert(dt2 == DateTime(2010, 12, 1, 12, 33, 33));
1105
1106         auto dt3 = DateTime(1999, 1, 29, 12, 33, 33);
1107         dt3.roll!"months"(1);
1108         assert(dt3 == DateTime(1999, 3, 1, 12, 33, 33));
1109
1110         auto dt4 = DateTime(1999, 1, 29, 12, 33, 33);
1111         dt4.roll!"months"(1, AllowDayOverflow.no);
1112         assert(dt4 == DateTime(1999, 2, 28, 12, 33, 33));
1113
1114         auto dt5 = DateTime(2000, 2, 29, 12, 30, 33);
1115         dt5.roll!"years"(1);
1116         assert(dt5 == DateTime(2001, 3, 1, 12, 30, 33));
1117
1118         auto dt6 = DateTime(2000, 2, 29, 12, 30, 33);
1119         dt6.roll!"years"(1, AllowDayOverflow.no);
1120         assert(dt6 == DateTime(2001, 2, 28, 12, 30, 33));
1121     }
1122
1123     @safe unittest
1124     {
1125         auto dt = DateTime(2000, 1, 31);
1126         dt.roll!"years"(7).roll!"months"(-4);
1127         assert(dt == DateTime(2007, 10, 1));
1128
1129         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
1130         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
1131         static assert(!__traits(compiles, cdt.roll!"years"(4)));
1132         static assert(!__traits(compiles, idt.roll!"years"(4)));
1133         static assert(!__traits(compiles, cdt.roll!"months"(4)));
1134         static assert(!__traits(compiles, idt.roll!"months"(4)));
1135     }
1136
1137
1138     /++
1139         Adds the given number of units to this $(LREF DateTime). A negative
1140         number will subtract.
1141
1142         The difference between rolling and adding is that rolling does not
1143         affect larger units. For instance, rolling a $(LREF DateTime) one
1144         year's worth of days gets the exact same $(LREF DateTime).
1145
1146         Accepted units are $(D "days"), $(D "minutes"), $(D "hours"),
1147         $(D "minutes"), and $(D "seconds").
1148
1149         Params:
1150             units = The units to add.
1151             value = The number of $(D_PARAM units) to add to this
1152                     $(LREF DateTime).
1153       +/
1154     ref DateTime roll(string units)(long value) @safe pure nothrow @nogc
1155         if (units == "days")
1156     {
1157         _date.roll!"days"(value);
1158         return this;
1159     }
1160
1161     ///
1162     @safe unittest
1163     {
1164         auto dt1 = DateTime(2010, 1, 1, 11, 23, 12);
1165         dt1.roll!"days"(1);
1166         assert(dt1 == DateTime(2010, 1, 2, 11, 23, 12));
1167         dt1.roll!"days"(365);
1168         assert(dt1 == DateTime(2010, 1, 26, 11, 23, 12));
1169         dt1.roll!"days"(-32);
1170         assert(dt1 == DateTime(2010, 1, 25, 11, 23, 12));
1171
1172         auto dt2 = DateTime(2010, 7, 4, 12, 0, 0);
1173         dt2.roll!"hours"(1);
1174         assert(dt2 == DateTime(2010, 7, 4, 13, 0, 0));
1175
1176         auto dt3 = DateTime(2010, 1, 1, 0, 0, 0);
1177         dt3.roll!"seconds"(-1);
1178         assert(dt3 == DateTime(2010, 1, 1, 0, 0, 59));
1179     }
1180
1181     @safe unittest
1182     {
1183         auto dt = DateTime(2000, 1, 31);
1184         dt.roll!"days"(7).roll!"days"(-4);
1185         assert(dt == DateTime(2000, 1, 3));
1186
1187         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
1188         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
1189         static assert(!__traits(compiles, cdt.roll!"days"(4)));
1190         static assert(!__traits(compiles, idt.roll!"days"(4)));
1191     }
1192
1193
1194     // Shares documentation with "days" version.
1195     ref DateTime roll(string units)(long value) @safe pure nothrow @nogc
1196         if (units == "hours" ||
1197             units == "minutes" ||
1198             units == "seconds")
1199     {
1200         _tod.roll!units(value);
1201         return this;
1202     }
1203
1204     // Test roll!"hours"().
1205     @safe unittest
1206     {
1207         static void testDT(DateTime orig, int hours, in DateTime expected, size_t line = __LINE__)
1208         {
1209             orig.roll!"hours"(hours);
1210             assert(orig == expected);
1211         }
1212
1213         // Test A.D.
1214         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 0,
1215                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1216         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1,
1217                DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)));
1218         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 2,
1219                DateTime(Date(1999, 7, 6), TimeOfDay(14, 30, 33)));
1220         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 3,
1221                DateTime(Date(1999, 7, 6), TimeOfDay(15, 30, 33)));
1222         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 4,
1223                DateTime(Date(1999, 7, 6), TimeOfDay(16, 30, 33)));
1224         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 5,
1225                DateTime(Date(1999, 7, 6), TimeOfDay(17, 30, 33)));
1226         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 6,
1227                DateTime(Date(1999, 7, 6), TimeOfDay(18, 30, 33)));
1228         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 7,
1229                DateTime(Date(1999, 7, 6), TimeOfDay(19, 30, 33)));
1230         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 8,
1231                DateTime(Date(1999, 7, 6), TimeOfDay(20, 30, 33)));
1232         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 9,
1233                DateTime(Date(1999, 7, 6), TimeOfDay(21, 30, 33)));
1234         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 10,
1235                DateTime(Date(1999, 7, 6), TimeOfDay(22, 30, 33)));
1236         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 11,
1237                DateTime(Date(1999, 7, 6), TimeOfDay(23, 30, 33)));
1238         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 12,
1239                DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)));
1240         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 13,
1241                DateTime(Date(1999, 7, 6), TimeOfDay(1, 30, 33)));
1242         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 14,
1243                DateTime(Date(1999, 7, 6), TimeOfDay(2, 30, 33)));
1244         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 15,
1245                DateTime(Date(1999, 7, 6), TimeOfDay(3, 30, 33)));
1246         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 16,
1247                DateTime(Date(1999, 7, 6), TimeOfDay(4, 30, 33)));
1248         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 17,
1249                DateTime(Date(1999, 7, 6), TimeOfDay(5, 30, 33)));
1250         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 18,
1251                DateTime(Date(1999, 7, 6), TimeOfDay(6, 30, 33)));
1252         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 19,
1253                DateTime(Date(1999, 7, 6), TimeOfDay(7, 30, 33)));
1254         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 20,
1255                DateTime(Date(1999, 7, 6), TimeOfDay(8, 30, 33)));
1256         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 21,
1257                DateTime(Date(1999, 7, 6), TimeOfDay(9, 30, 33)));
1258         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 22,
1259                DateTime(Date(1999, 7, 6), TimeOfDay(10, 30, 33)));
1260         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 23,
1261                DateTime(Date(1999, 7, 6), TimeOfDay(11, 30, 33)));
1262         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 24,
1263                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1264         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 25,
1265                DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)));
1266
1267         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -1,
1268                DateTime(Date(1999, 7, 6), TimeOfDay(11, 30, 33)));
1269         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -2,
1270                DateTime(Date(1999, 7, 6), TimeOfDay(10, 30, 33)));
1271         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -3,
1272                DateTime(Date(1999, 7, 6), TimeOfDay(9, 30, 33)));
1273         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -4,
1274                DateTime(Date(1999, 7, 6), TimeOfDay(8, 30, 33)));
1275         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -5,
1276                DateTime(Date(1999, 7, 6), TimeOfDay(7, 30, 33)));
1277         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -6,
1278                DateTime(Date(1999, 7, 6), TimeOfDay(6, 30, 33)));
1279         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -7,
1280                DateTime(Date(1999, 7, 6), TimeOfDay(5, 30, 33)));
1281         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -8,
1282                DateTime(Date(1999, 7, 6), TimeOfDay(4, 30, 33)));
1283         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -9,
1284                DateTime(Date(1999, 7, 6), TimeOfDay(3, 30, 33)));
1285         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -10,
1286                DateTime(Date(1999, 7, 6), TimeOfDay(2, 30, 33)));
1287         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -11,
1288                DateTime(Date(1999, 7, 6), TimeOfDay(1, 30, 33)));
1289         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -12,
1290                DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)));
1291         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -13,
1292                DateTime(Date(1999, 7, 6), TimeOfDay(23, 30, 33)));
1293         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -14,
1294                DateTime(Date(1999, 7, 6), TimeOfDay(22, 30, 33)));
1295         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -15,
1296                DateTime(Date(1999, 7, 6), TimeOfDay(21, 30, 33)));
1297         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -16,
1298                DateTime(Date(1999, 7, 6), TimeOfDay(20, 30, 33)));
1299         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -17,
1300                DateTime(Date(1999, 7, 6), TimeOfDay(19, 30, 33)));
1301         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -18,
1302                DateTime(Date(1999, 7, 6), TimeOfDay(18, 30, 33)));
1303         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -19,
1304                DateTime(Date(1999, 7, 6), TimeOfDay(17, 30, 33)));
1305         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -20,
1306                DateTime(Date(1999, 7, 6), TimeOfDay(16, 30, 33)));
1307         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -21,
1308                DateTime(Date(1999, 7, 6), TimeOfDay(15, 30, 33)));
1309         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -22,
1310                DateTime(Date(1999, 7, 6), TimeOfDay(14, 30, 33)));
1311         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -23,
1312                DateTime(Date(1999, 7, 6), TimeOfDay(13, 30, 33)));
1313         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -24,
1314                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1315         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -25,
1316                DateTime(Date(1999, 7, 6), TimeOfDay(11, 30, 33)));
1317
1318         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)), 1,
1319                DateTime(Date(1999, 7, 6), TimeOfDay(1, 30, 33)));
1320         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)), 0,
1321                DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)));
1322         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)), -1,
1323                DateTime(Date(1999, 7, 6), TimeOfDay(23, 30, 33)));
1324
1325         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(23, 30, 33)), 1,
1326                DateTime(Date(1999, 7, 6), TimeOfDay(0, 30, 33)));
1327         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(23, 30, 33)), 0,
1328                DateTime(Date(1999, 7, 6), TimeOfDay(23, 30, 33)));
1329         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(23, 30, 33)), -1,
1330                DateTime(Date(1999, 7, 6), TimeOfDay(22, 30, 33)));
1331
1332         testDT(DateTime(Date(1999, 7, 31), TimeOfDay(23, 30, 33)), 1,
1333                DateTime(Date(1999, 7, 31), TimeOfDay(0, 30, 33)));
1334         testDT(DateTime(Date(1999, 8, 1), TimeOfDay(0, 30, 33)), -1,
1335                DateTime(Date(1999, 8, 1), TimeOfDay(23, 30, 33)));
1336
1337         testDT(DateTime(Date(1999, 12, 31), TimeOfDay(23, 30, 33)), 1,
1338                DateTime(Date(1999, 12, 31), TimeOfDay(0, 30, 33)));
1339         testDT(DateTime(Date(2000, 1, 1), TimeOfDay(0, 30, 33)), -1,
1340                DateTime(Date(2000, 1, 1), TimeOfDay(23, 30, 33)));
1341
1342         testDT(DateTime(Date(1999, 2, 28), TimeOfDay(23, 30, 33)), 25,
1343                DateTime(Date(1999, 2, 28), TimeOfDay(0, 30, 33)));
1344         testDT(DateTime(Date(1999, 3, 2), TimeOfDay(0, 30, 33)), -25,
1345                DateTime(Date(1999, 3, 2), TimeOfDay(23, 30, 33)));
1346
1347         testDT(DateTime(Date(2000, 2, 28), TimeOfDay(23, 30, 33)), 25,
1348                DateTime(Date(2000, 2, 28), TimeOfDay(0, 30, 33)));
1349         testDT(DateTime(Date(2000, 3, 1), TimeOfDay(0, 30, 33)), -25,
1350                DateTime(Date(2000, 3, 1), TimeOfDay(23, 30, 33)));
1351
1352         // Test B.C.
1353         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 0,
1354                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1355         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1,
1356                DateTime(Date(-1999, 7, 6), TimeOfDay(13, 30, 33)));
1357         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 2,
1358                DateTime(Date(-1999, 7, 6), TimeOfDay(14, 30, 33)));
1359         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 3,
1360                DateTime(Date(-1999, 7, 6), TimeOfDay(15, 30, 33)));
1361         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 4,
1362                DateTime(Date(-1999, 7, 6), TimeOfDay(16, 30, 33)));
1363         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 5,
1364                DateTime(Date(-1999, 7, 6), TimeOfDay(17, 30, 33)));
1365         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 6,
1366                DateTime(Date(-1999, 7, 6), TimeOfDay(18, 30, 33)));
1367         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 7,
1368                DateTime(Date(-1999, 7, 6), TimeOfDay(19, 30, 33)));
1369         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 8,
1370                DateTime(Date(-1999, 7, 6), TimeOfDay(20, 30, 33)));
1371         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 9,
1372                DateTime(Date(-1999, 7, 6), TimeOfDay(21, 30, 33)));
1373         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 10,
1374                DateTime(Date(-1999, 7, 6), TimeOfDay(22, 30, 33)));
1375         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 11,
1376                DateTime(Date(-1999, 7, 6), TimeOfDay(23, 30, 33)));
1377         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 12,
1378                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 30, 33)));
1379         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 13,
1380                DateTime(Date(-1999, 7, 6), TimeOfDay(1, 30, 33)));
1381         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 14,
1382                DateTime(Date(-1999, 7, 6), TimeOfDay(2, 30, 33)));
1383         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 15,
1384                DateTime(Date(-1999, 7, 6), TimeOfDay(3, 30, 33)));
1385         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 16,
1386                DateTime(Date(-1999, 7, 6), TimeOfDay(4, 30, 33)));
1387         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 17,
1388                DateTime(Date(-1999, 7, 6), TimeOfDay(5, 30, 33)));
1389         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 18,
1390                DateTime(Date(-1999, 7, 6), TimeOfDay(6, 30, 33)));
1391         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 19,
1392                DateTime(Date(-1999, 7, 6), TimeOfDay(7, 30, 33)));
1393         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 20,
1394                DateTime(Date(-1999, 7, 6), TimeOfDay(8, 30, 33)));
1395         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 21,
1396                DateTime(Date(-1999, 7, 6), TimeOfDay(9, 30, 33)));
1397         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 22,
1398                DateTime(Date(-1999, 7, 6), TimeOfDay(10, 30, 33)));
1399         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 23,
1400                DateTime(Date(-1999, 7, 6), TimeOfDay(11, 30, 33)));
1401         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 24,
1402                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1403         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 25,
1404                DateTime(Date(-1999, 7, 6), TimeOfDay(13, 30, 33)));
1405
1406         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -1,
1407                DateTime(Date(-1999, 7, 6), TimeOfDay(11, 30, 33)));
1408         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -2,
1409                DateTime(Date(-1999, 7, 6), TimeOfDay(10, 30, 33)));
1410         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -3,
1411                DateTime(Date(-1999, 7, 6), TimeOfDay(9, 30, 33)));
1412         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -4,
1413                DateTime(Date(-1999, 7, 6), TimeOfDay(8, 30, 33)));
1414         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -5,
1415                DateTime(Date(-1999, 7, 6), TimeOfDay(7, 30, 33)));
1416         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -6,
1417                DateTime(Date(-1999, 7, 6), TimeOfDay(6, 30, 33)));
1418         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -7,
1419                DateTime(Date(-1999, 7, 6), TimeOfDay(5, 30, 33)));
1420         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -8,
1421                DateTime(Date(-1999, 7, 6), TimeOfDay(4, 30, 33)));
1422         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -9,
1423                DateTime(Date(-1999, 7, 6), TimeOfDay(3, 30, 33)));
1424         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -10,
1425                DateTime(Date(-1999, 7, 6), TimeOfDay(2, 30, 33)));
1426         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -11,
1427                DateTime(Date(-1999, 7, 6), TimeOfDay(1, 30, 33)));
1428         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -12,
1429                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 30, 33)));
1430         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -13,
1431                DateTime(Date(-1999, 7, 6), TimeOfDay(23, 30, 33)));
1432         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -14,
1433                DateTime(Date(-1999, 7, 6), TimeOfDay(22, 30, 33)));
1434         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -15,
1435                DateTime(Date(-1999, 7, 6), TimeOfDay(21, 30, 33)));
1436         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -16,
1437                DateTime(Date(-1999, 7, 6), TimeOfDay(20, 30, 33)));
1438         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -17,
1439                DateTime(Date(-1999, 7, 6), TimeOfDay(19, 30, 33)));
1440         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -18,
1441                DateTime(Date(-1999, 7, 6), TimeOfDay(18, 30, 33)));
1442         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -19,
1443                DateTime(Date(-1999, 7, 6), TimeOfDay(17, 30, 33)));
1444         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -20,
1445                DateTime(Date(-1999, 7, 6), TimeOfDay(16, 30, 33)));
1446         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -21,
1447                DateTime(Date(-1999, 7, 6), TimeOfDay(15, 30, 33)));
1448         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -22,
1449                DateTime(Date(-1999, 7, 6), TimeOfDay(14, 30, 33)));
1450         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -23,
1451                DateTime(Date(-1999, 7, 6), TimeOfDay(13, 30, 33)));
1452         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -24,
1453                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1454         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -25,
1455                DateTime(Date(-1999, 7, 6), TimeOfDay(11, 30, 33)));
1456
1457         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 30, 33)), 1,
1458                DateTime(Date(-1999, 7, 6), TimeOfDay(1, 30, 33)));
1459         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 30, 33)), 0,
1460                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 30, 33)));
1461         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 30, 33)), -1,
1462                DateTime(Date(-1999, 7, 6), TimeOfDay(23, 30, 33)));
1463
1464         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(23, 30, 33)), 1,
1465                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 30, 33)));
1466         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(23, 30, 33)), 0,
1467                DateTime(Date(-1999, 7, 6), TimeOfDay(23, 30, 33)));
1468         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(23, 30, 33)), -1,
1469                DateTime(Date(-1999, 7, 6), TimeOfDay(22, 30, 33)));
1470
1471         testDT(DateTime(Date(-1999, 7, 31), TimeOfDay(23, 30, 33)), 1,
1472                DateTime(Date(-1999, 7, 31), TimeOfDay(0, 30, 33)));
1473         testDT(DateTime(Date(-1999, 8, 1), TimeOfDay(0, 30, 33)), -1,
1474                DateTime(Date(-1999, 8, 1), TimeOfDay(23, 30, 33)));
1475
1476         testDT(DateTime(Date(-2001, 12, 31), TimeOfDay(23, 30, 33)), 1,
1477                DateTime(Date(-2001, 12, 31), TimeOfDay(0, 30, 33)));
1478         testDT(DateTime(Date(-2000, 1, 1), TimeOfDay(0, 30, 33)), -1,
1479                DateTime(Date(-2000, 1, 1), TimeOfDay(23, 30, 33)));
1480
1481         testDT(DateTime(Date(-2001, 2, 28), TimeOfDay(23, 30, 33)), 25,
1482                DateTime(Date(-2001, 2, 28), TimeOfDay(0, 30, 33)));
1483         testDT(DateTime(Date(-2001, 3, 2), TimeOfDay(0, 30, 33)), -25,
1484                DateTime(Date(-2001, 3, 2), TimeOfDay(23, 30, 33)));
1485
1486         testDT(DateTime(Date(-2000, 2, 28), TimeOfDay(23, 30, 33)), 25,
1487                DateTime(Date(-2000, 2, 28), TimeOfDay(0, 30, 33)));
1488         testDT(DateTime(Date(-2000, 3, 1), TimeOfDay(0, 30, 33)), -25,
1489                DateTime(Date(-2000, 3, 1), TimeOfDay(23, 30, 33)));
1490
1491         // Test Both
1492         testDT(DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 33)), 17_546,
1493                DateTime(Date(-1, 1, 1), TimeOfDay(13, 30, 33)));
1494         testDT(DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 33)), -17_546,
1495                DateTime(Date(1, 1, 1), TimeOfDay(11, 30, 33)));
1496
1497         auto dt = DateTime(2000, 1, 31, 9, 7, 6);
1498         dt.roll!"hours"(27).roll!"hours"(-9);
1499         assert(dt == DateTime(2000, 1, 31, 3, 7, 6));
1500
1501         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
1502         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
1503         static assert(!__traits(compiles, cdt.roll!"hours"(4)));
1504         static assert(!__traits(compiles, idt.roll!"hours"(4)));
1505     }
1506
1507     // Test roll!"minutes"().
1508     @safe unittest
1509     {
1510         static void testDT(DateTime orig, int minutes, in DateTime expected, size_t line = __LINE__)
1511         {
1512             orig.roll!"minutes"(minutes);
1513             assert(orig == expected);
1514         }
1515
1516         // Test A.D.
1517         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 0,
1518                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1519         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1,
1520                DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)));
1521         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 2,
1522                DateTime(Date(1999, 7, 6), TimeOfDay(12, 32, 33)));
1523         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 3,
1524                DateTime(Date(1999, 7, 6), TimeOfDay(12, 33, 33)));
1525         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 4,
1526                DateTime(Date(1999, 7, 6), TimeOfDay(12, 34, 33)));
1527         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 5,
1528                DateTime(Date(1999, 7, 6), TimeOfDay(12, 35, 33)));
1529         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 10,
1530                DateTime(Date(1999, 7, 6), TimeOfDay(12, 40, 33)));
1531         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 15,
1532                DateTime(Date(1999, 7, 6), TimeOfDay(12, 45, 33)));
1533         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 29,
1534                DateTime(Date(1999, 7, 6), TimeOfDay(12, 59, 33)));
1535         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 30,
1536                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)));
1537         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 45,
1538                DateTime(Date(1999, 7, 6), TimeOfDay(12, 15, 33)));
1539         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 60,
1540                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1541         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 75,
1542                DateTime(Date(1999, 7, 6), TimeOfDay(12, 45, 33)));
1543         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 90,
1544                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)));
1545         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 100,
1546                DateTime(Date(1999, 7, 6), TimeOfDay(12, 10, 33)));
1547
1548         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 689,
1549                DateTime(Date(1999, 7, 6), TimeOfDay(12, 59, 33)));
1550         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 690,
1551                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)));
1552         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 691,
1553                DateTime(Date(1999, 7, 6), TimeOfDay(12, 1, 33)));
1554         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 960,
1555                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1556         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1439,
1557                DateTime(Date(1999, 7, 6), TimeOfDay(12, 29, 33)));
1558         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1440,
1559                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1560         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1441,
1561                DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)));
1562         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 2880,
1563                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1564
1565         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -1,
1566                DateTime(Date(1999, 7, 6), TimeOfDay(12, 29, 33)));
1567         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -2,
1568                DateTime(Date(1999, 7, 6), TimeOfDay(12, 28, 33)));
1569         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -3,
1570                DateTime(Date(1999, 7, 6), TimeOfDay(12, 27, 33)));
1571         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -4,
1572                DateTime(Date(1999, 7, 6), TimeOfDay(12, 26, 33)));
1573         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -5,
1574                DateTime(Date(1999, 7, 6), TimeOfDay(12, 25, 33)));
1575         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -10,
1576                DateTime(Date(1999, 7, 6), TimeOfDay(12, 20, 33)));
1577         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -15,
1578                DateTime(Date(1999, 7, 6), TimeOfDay(12, 15, 33)));
1579         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -29,
1580                DateTime(Date(1999, 7, 6), TimeOfDay(12, 1, 33)));
1581         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -30,
1582                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)));
1583         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -45,
1584                DateTime(Date(1999, 7, 6), TimeOfDay(12, 45, 33)));
1585         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -60,
1586                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1587         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -75,
1588                DateTime(Date(1999, 7, 6), TimeOfDay(12, 15, 33)));
1589         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -90,
1590                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)));
1591         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -100,
1592                DateTime(Date(1999, 7, 6), TimeOfDay(12, 50, 33)));
1593
1594         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -749,
1595                DateTime(Date(1999, 7, 6), TimeOfDay(12, 1, 33)));
1596         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -750,
1597                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)));
1598         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -751,
1599                DateTime(Date(1999, 7, 6), TimeOfDay(12, 59, 33)));
1600         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -960,
1601                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1602         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -1439,
1603                DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)));
1604         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -1440,
1605                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1606         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -1441,
1607                DateTime(Date(1999, 7, 6), TimeOfDay(12, 29, 33)));
1608         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -2880,
1609                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1610
1611         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)), 1,
1612                DateTime(Date(1999, 7, 6), TimeOfDay(12, 1, 33)));
1613         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)), 0,
1614                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)));
1615         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 33)), -1,
1616                DateTime(Date(1999, 7, 6), TimeOfDay(12, 59, 33)));
1617
1618         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(11, 59, 33)), 1,
1619                DateTime(Date(1999, 7, 6), TimeOfDay(11, 0, 33)));
1620         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(11, 59, 33)), 0,
1621                DateTime(Date(1999, 7, 6), TimeOfDay(11, 59, 33)));
1622         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(11, 59, 33)), -1,
1623                DateTime(Date(1999, 7, 6), TimeOfDay(11, 58, 33)));
1624
1625         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33)), 1,
1626                DateTime(Date(1999, 7, 6), TimeOfDay(0, 1, 33)));
1627         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33)), 0,
1628                DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33)));
1629         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 33)), -1,
1630                DateTime(Date(1999, 7, 6), TimeOfDay(0, 59, 33)));
1631
1632         testDT(DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 33)), 1,
1633                DateTime(Date(1999, 7, 5), TimeOfDay(23, 0, 33)));
1634         testDT(DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 33)), 0,
1635                DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 33)));
1636         testDT(DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 33)), -1,
1637                DateTime(Date(1999, 7, 5), TimeOfDay(23, 58, 33)));
1638
1639         testDT(DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 33)), 1,
1640                DateTime(Date(1998, 12, 31), TimeOfDay(23, 0, 33)));
1641         testDT(DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 33)), 0,
1642                DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 33)));
1643         testDT(DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 33)), -1,
1644                DateTime(Date(1998, 12, 31), TimeOfDay(23, 58, 33)));
1645
1646         // Test B.C.
1647         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 0,
1648                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1649         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1,
1650                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 31, 33)));
1651         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 2,
1652                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 32, 33)));
1653         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 3,
1654                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 33, 33)));
1655         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 4,
1656                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 34, 33)));
1657         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 5,
1658                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 35, 33)));
1659         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 10,
1660                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 40, 33)));
1661         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 15,
1662                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 45, 33)));
1663         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 29,
1664                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 59, 33)));
1665         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 30,
1666                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)));
1667         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 45,
1668                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 15, 33)));
1669         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 60,
1670                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1671         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 75,
1672                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 45, 33)));
1673         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 90,
1674                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)));
1675         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 100,
1676                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 10, 33)));
1677
1678         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 689,
1679                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 59, 33)));
1680         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 690,
1681                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)));
1682         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 691,
1683                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 1, 33)));
1684         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 960,
1685                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1686         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1439,
1687                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 29, 33)));
1688         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1440,
1689                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1690         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1441,
1691                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 31, 33)));
1692         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 2880,
1693                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1694
1695         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -1,
1696                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 29, 33)));
1697         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -2,
1698                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 28, 33)));
1699         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -3,
1700                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 27, 33)));
1701         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -4,
1702                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 26, 33)));
1703         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -5,
1704                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 25, 33)));
1705         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -10,
1706                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 20, 33)));
1707         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -15,
1708                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 15, 33)));
1709         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -29,
1710                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 1, 33)));
1711         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -30,
1712                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)));
1713         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -45,
1714                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 45, 33)));
1715         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -60,
1716                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1717         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -75,
1718                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 15, 33)));
1719         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -90,
1720                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)));
1721         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -100,
1722                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 50, 33)));
1723
1724         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -749,
1725                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 1, 33)));
1726         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -750,
1727                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)));
1728         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -751,
1729                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 59, 33)));
1730         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -960,
1731                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1732         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -1439,
1733                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 31, 33)));
1734         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -1440,
1735                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1736         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -1441,
1737                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 29, 33)));
1738         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -2880,
1739                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1740
1741         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)), 1,
1742                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 1, 33)));
1743         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)), 0,
1744                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)));
1745         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 33)), -1,
1746                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 59, 33)));
1747
1748         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(11, 59, 33)), 1,
1749                DateTime(Date(-1999, 7, 6), TimeOfDay(11, 0, 33)));
1750         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(11, 59, 33)), 0,
1751                DateTime(Date(-1999, 7, 6), TimeOfDay(11, 59, 33)));
1752         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(11, 59, 33)), -1,
1753                DateTime(Date(-1999, 7, 6), TimeOfDay(11, 58, 33)));
1754
1755         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 33)), 1,
1756                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 1, 33)));
1757         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 33)), 0,
1758                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 33)));
1759         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 33)), -1,
1760                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 59, 33)));
1761
1762         testDT(DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 33)), 1,
1763                DateTime(Date(-1999, 7, 5), TimeOfDay(23, 0, 33)));
1764         testDT(DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 33)), 0,
1765                DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 33)));
1766         testDT(DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 33)), -1,
1767                DateTime(Date(-1999, 7, 5), TimeOfDay(23, 58, 33)));
1768
1769         testDT(DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 33)), 1,
1770                DateTime(Date(-2000, 12, 31), TimeOfDay(23, 0, 33)));
1771         testDT(DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 33)), 0,
1772                DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 33)));
1773         testDT(DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 33)), -1,
1774                DateTime(Date(-2000, 12, 31), TimeOfDay(23, 58, 33)));
1775
1776         // Test Both
1777         testDT(DateTime(Date(1, 1, 1), TimeOfDay(0, 0, 0)), -1,
1778                DateTime(Date(1, 1, 1), TimeOfDay(0, 59, 0)));
1779         testDT(DateTime(Date(0, 12, 31), TimeOfDay(23, 59, 0)), 1,
1780                DateTime(Date(0, 12, 31), TimeOfDay(23, 0, 0)));
1781
1782         testDT(DateTime(Date(0, 1, 1), TimeOfDay(0, 0, 0)), -1,
1783                DateTime(Date(0, 1, 1), TimeOfDay(0, 59, 0)));
1784         testDT(DateTime(Date(-1, 12, 31), TimeOfDay(23, 59, 0)), 1,
1785                DateTime(Date(-1, 12, 31), TimeOfDay(23, 0, 0)));
1786
1787         testDT(DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 33)), 1_052_760,
1788                DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 33)));
1789         testDT(DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 33)), -1_052_760,
1790                DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 33)));
1791
1792         testDT(DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 33)), 1_052_782,
1793                DateTime(Date(-1, 1, 1), TimeOfDay(11, 52, 33)));
1794         testDT(DateTime(Date(1, 1, 1), TimeOfDay(13, 52, 33)), -1_052_782,
1795                DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 33)));
1796
1797         auto dt = DateTime(2000, 1, 31, 9, 7, 6);
1798         dt.roll!"minutes"(92).roll!"minutes"(-292);
1799         assert(dt == DateTime(2000, 1, 31, 9, 47, 6));
1800
1801         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
1802         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
1803         static assert(!__traits(compiles, cdt.roll!"minutes"(4)));
1804         static assert(!__traits(compiles, idt.roll!"minutes"(4)));
1805     }
1806
1807     // Test roll!"seconds"().
1808     @safe unittest
1809     {
1810         static void testDT(DateTime orig, int seconds, in DateTime expected, size_t line = __LINE__)
1811         {
1812             orig.roll!"seconds"(seconds);
1813             assert(orig == expected);
1814         }
1815
1816         // Test A.D.
1817         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 0,
1818                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1819         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1,
1820                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)));
1821         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 2,
1822                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 35)));
1823         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 3,
1824                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 36)));
1825         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 4,
1826                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 37)));
1827         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 5,
1828                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 38)));
1829         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 10,
1830                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 43)));
1831         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 15,
1832                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 48)));
1833         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 26,
1834                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 59)));
1835         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 27,
1836                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)));
1837         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 30,
1838                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 3)));
1839         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 59,
1840                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 32)));
1841         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 60,
1842                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1843         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 61,
1844                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)));
1845
1846         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1766,
1847                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 59)));
1848         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1767,
1849                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)));
1850         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 1768,
1851                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 1)));
1852         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 2007,
1853                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)));
1854         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 3599,
1855                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 32)));
1856         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 3600,
1857                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1858         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 3601,
1859                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)));
1860         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), 7200,
1861                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1862
1863         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -1,
1864                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 32)));
1865         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -2,
1866                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 31)));
1867         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -3,
1868                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 30)));
1869         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -4,
1870                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 29)));
1871         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -5,
1872                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 28)));
1873         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -10,
1874                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 23)));
1875         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -15,
1876                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 18)));
1877         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -33,
1878                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)));
1879         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -34,
1880                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 59)));
1881         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -35,
1882                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 58)));
1883         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -59,
1884                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)));
1885         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -60,
1886                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
1887         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)), -61,
1888                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 32)));
1889
1890         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)), 1,
1891                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 1)));
1892         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)), 0,
1893                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)));
1894         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 0)), -1,
1895                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 59)));
1896
1897         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0)), 1,
1898                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 1)));
1899         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0)), 0,
1900                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0)));
1901         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 0)), -1,
1902                DateTime(Date(1999, 7, 6), TimeOfDay(12, 0, 59)));
1903
1904         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), 1,
1905                DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 1)));
1906         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), 0,
1907                DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)));
1908         testDT(DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 0)), -1,
1909                DateTime(Date(1999, 7, 6), TimeOfDay(0, 0, 59)));
1910
1911         testDT(DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 59)), 1,
1912                DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 0)));
1913         testDT(DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 59)), 0,
1914                DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 59)));
1915         testDT(DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 59)), -1,
1916                DateTime(Date(1999, 7, 5), TimeOfDay(23, 59, 58)));
1917
1918         testDT(DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 59)), 1,
1919                DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 0)));
1920         testDT(DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 59)), 0,
1921                DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 59)));
1922         testDT(DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 59)), -1,
1923                DateTime(Date(1998, 12, 31), TimeOfDay(23, 59, 58)));
1924
1925         // Test B.C.
1926         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 0,
1927                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1928         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1,
1929                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 34)));
1930         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 2,
1931                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 35)));
1932         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 3,
1933                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 36)));
1934         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 4,
1935                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 37)));
1936         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 5,
1937                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 38)));
1938         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 10,
1939                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 43)));
1940         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 15,
1941                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 48)));
1942         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 26,
1943                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 59)));
1944         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 27,
1945                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)));
1946         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 30,
1947                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 3)));
1948         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 59,
1949                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 32)));
1950         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 60,
1951                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1952         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 61,
1953                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 34)));
1954
1955         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1766,
1956                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 59)));
1957         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1767,
1958                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)));
1959         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 1768,
1960                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 1)));
1961         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 2007,
1962                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)));
1963         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 3599,
1964                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 32)));
1965         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 3600,
1966                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1967         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 3601,
1968                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 34)));
1969         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), 7200,
1970                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1971
1972         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -1,
1973                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 32)));
1974         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -2,
1975                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 31)));
1976         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -3,
1977                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 30)));
1978         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -4,
1979                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 29)));
1980         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -5,
1981                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 28)));
1982         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -10,
1983                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 23)));
1984         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -15,
1985                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 18)));
1986         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -33,
1987                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)));
1988         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -34,
1989                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 59)));
1990         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -35,
1991                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 58)));
1992         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -59,
1993                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 34)));
1994         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -60,
1995                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
1996         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)), -61,
1997                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 32)));
1998
1999         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)), 1,
2000                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 1)));
2001         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)), 0,
2002                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)));
2003         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 0)), -1,
2004                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 59)));
2005
2006         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 0)), 1,
2007                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 1)));
2008         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 0)), 0,
2009                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 0)));
2010         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 0)), -1,
2011                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 0, 59)));
2012
2013         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 0)), 1,
2014                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 1)));
2015         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 0)), 0,
2016                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 0)));
2017         testDT(DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 0)), -1,
2018                DateTime(Date(-1999, 7, 6), TimeOfDay(0, 0, 59)));
2019
2020         testDT(DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 59)), 1,
2021                DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 0)));
2022         testDT(DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 59)), 0,
2023                DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 59)));
2024         testDT(DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 59)), -1,
2025                DateTime(Date(-1999, 7, 5), TimeOfDay(23, 59, 58)));
2026
2027         testDT(DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 59)), 1,
2028                DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 0)));
2029         testDT(DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 59)), 0,
2030                DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 59)));
2031         testDT(DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 59)), -1,
2032                DateTime(Date(-2000, 12, 31), TimeOfDay(23, 59, 58)));
2033
2034         // Test Both
2035         testDT(DateTime(Date(1, 1, 1), TimeOfDay(0, 0, 0)), -1,
2036                DateTime(Date(1, 1, 1), TimeOfDay(0, 0, 59)));
2037         testDT(DateTime(Date(0, 12, 31), TimeOfDay(23, 59, 59)), 1,
2038                DateTime(Date(0, 12, 31), TimeOfDay(23, 59, 0)));
2039
2040         testDT(DateTime(Date(0, 1, 1), TimeOfDay(0, 0, 0)), -1,
2041                DateTime(Date(0, 1, 1), TimeOfDay(0, 0, 59)));
2042         testDT(DateTime(Date(-1, 12, 31), TimeOfDay(23, 59, 59)), 1,
2043                DateTime(Date(-1, 12, 31), TimeOfDay(23, 59, 0)));
2044
2045         testDT(DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 33)), 63_165_600L,
2046                DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 33)));
2047         testDT(DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 33)), -63_165_600L,
2048                DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 33)));
2049
2050         testDT(DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 33)), 63_165_617L,
2051                DateTime(Date(-1, 1, 1), TimeOfDay(11, 30, 50)));
2052         testDT(DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 50)), -63_165_617L,
2053                DateTime(Date(1, 1, 1), TimeOfDay(13, 30, 33)));
2054
2055         auto dt = DateTime(2000, 1, 31, 9, 7, 6);
2056         dt.roll!"seconds"(92).roll!"seconds"(-292);
2057         assert(dt == DateTime(2000, 1, 31, 9, 7, 46));
2058
2059         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
2060         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
2061         static assert(!__traits(compiles, cdt.roll!"seconds"(4)));
2062         static assert(!__traits(compiles, idt.roll!"seconds"(4)));
2063     }
2064
2065
2066     /++
2067         Gives the result of adding or subtracting a $(REF Duration, core,time)
2068         from this $(LREF DateTime).
2069
2070         The legal types of arithmetic for $(LREF DateTime) using this operator
2071         are
2072
2073         $(BOOKTABLE,
2074         $(TR $(TD DateTime) $(TD +) $(TD Duration) $(TD -->) $(TD DateTime))
2075         $(TR $(TD DateTime) $(TD -) $(TD Duration) $(TD -->) $(TD DateTime))
2076         )
2077
2078         Params:
2079             duration = The $(REF Duration, core,time) to add to or subtract from
2080                        this $(LREF DateTime).
2081       +/
2082     DateTime opBinary(string op)(Duration duration) const @safe pure nothrow @nogc
2083         if (op == "+" || op == "-")
2084     {
2085         DateTime retval = this;
2086         immutable seconds = duration.total!"seconds";
2087         mixin("return retval._addSeconds(" ~ op ~ "seconds);");
2088     }
2089
2090     ///
2091     @safe unittest
2092     {
2093         import core.time : hours, seconds;
2094
2095         assert(DateTime(2015, 12, 31, 23, 59, 59) + seconds(1) ==
2096                DateTime(2016, 1, 1, 0, 0, 0));
2097
2098         assert(DateTime(2015, 12, 31, 23, 59, 59) + hours(1) ==
2099                DateTime(2016, 1, 1, 0, 59, 59));
2100
2101         assert(DateTime(2016, 1, 1, 0, 0, 0) - seconds(1) ==
2102                DateTime(2015, 12, 31, 23, 59, 59));
2103
2104         assert(DateTime(2016, 1, 1, 0, 59, 59) - hours(1) ==
2105                DateTime(2015, 12, 31, 23, 59, 59));
2106     }
2107
2108     @safe unittest
2109     {
2110         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2111
2112         assert(dt + dur!"weeks"(7) == DateTime(Date(1999, 8, 24), TimeOfDay(12, 30, 33)));
2113         assert(dt + dur!"weeks"(-7) == DateTime(Date(1999, 5, 18), TimeOfDay(12, 30, 33)));
2114         assert(dt + dur!"days"(7) == DateTime(Date(1999, 7, 13), TimeOfDay(12, 30, 33)));
2115         assert(dt + dur!"days"(-7) == DateTime(Date(1999, 6, 29), TimeOfDay(12, 30, 33)));
2116
2117         assert(dt + dur!"hours"(7) == DateTime(Date(1999, 7, 6), TimeOfDay(19, 30, 33)));
2118         assert(dt + dur!"hours"(-7) == DateTime(Date(1999, 7, 6), TimeOfDay(5, 30, 33)));
2119         assert(dt + dur!"minutes"(7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 37, 33)));
2120         assert(dt + dur!"minutes"(-7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 23, 33)));
2121         assert(dt + dur!"seconds"(7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2122         assert(dt + dur!"seconds"(-7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2123         assert(dt + dur!"msecs"(7_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2124         assert(dt + dur!"msecs"(-7_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2125         assert(dt + dur!"usecs"(7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2126         assert(dt + dur!"usecs"(-7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2127         assert(dt + dur!"hnsecs"(70_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2128         assert(dt + dur!"hnsecs"(-70_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2129
2130         assert(dt - dur!"weeks"(-7) == DateTime(Date(1999, 8, 24), TimeOfDay(12, 30, 33)));
2131         assert(dt - dur!"weeks"(7) == DateTime(Date(1999, 5, 18), TimeOfDay(12, 30, 33)));
2132         assert(dt - dur!"days"(-7) == DateTime(Date(1999, 7, 13), TimeOfDay(12, 30, 33)));
2133         assert(dt - dur!"days"(7) == DateTime(Date(1999, 6, 29), TimeOfDay(12, 30, 33)));
2134
2135         assert(dt - dur!"hours"(-7) == DateTime(Date(1999, 7, 6), TimeOfDay(19, 30, 33)));
2136         assert(dt - dur!"hours"(7) == DateTime(Date(1999, 7, 6), TimeOfDay(5, 30, 33)));
2137         assert(dt - dur!"minutes"(-7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 37, 33)));
2138         assert(dt - dur!"minutes"(7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 23, 33)));
2139         assert(dt - dur!"seconds"(-7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2140         assert(dt - dur!"seconds"(7) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2141         assert(dt - dur!"msecs"(-7_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2142         assert(dt - dur!"msecs"(7_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2143         assert(dt - dur!"usecs"(-7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2144         assert(dt - dur!"usecs"(7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2145         assert(dt - dur!"hnsecs"(-70_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2146         assert(dt - dur!"hnsecs"(70_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2147
2148         auto duration = dur!"seconds"(12);
2149         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2150         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2151         assert(cdt + duration == DateTime(1999, 7, 6, 12, 30, 45));
2152         assert(idt + duration == DateTime(1999, 7, 6, 12, 30, 45));
2153         assert(cdt - duration == DateTime(1999, 7, 6, 12, 30, 21));
2154         assert(idt - duration == DateTime(1999, 7, 6, 12, 30, 21));
2155     }
2156
2157     // Explicitly undocumented. It will be removed in January 2018. @@@DEPRECATED_2018-01@@@
2158     deprecated("Use Duration instead of TickDuration.")
2159     DateTime opBinary(string op)(in TickDuration td) const @safe pure nothrow @nogc
2160         if (op == "+" || op == "-")
2161     {
2162         DateTime retval = this;
2163         immutable seconds = td.seconds;
2164         mixin("return retval._addSeconds(" ~ op ~ "seconds);");
2165     }
2166
2167     deprecated @safe unittest
2168     {
2169         // This probably only runs in cases where gettimeofday() is used, but it's
2170         // hard to do this test correctly with variable ticksPerSec.
2171         if (TickDuration.ticksPerSec == 1_000_000)
2172         {
2173             auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2174
2175             assert(dt + TickDuration.from!"usecs"(7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2176             assert(dt + TickDuration.from!"usecs"(-7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2177
2178             assert(dt - TickDuration.from!"usecs"(-7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2179             assert(dt - TickDuration.from!"usecs"(7_000_000) == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2180         }
2181     }
2182
2183
2184     /++
2185         Gives the result of adding or subtracting a duration from this
2186         $(LREF DateTime), as well as assigning the result to this
2187         $(LREF DateTime).
2188
2189         The legal types of arithmetic for $(LREF DateTime) using this operator
2190         are
2191
2192         $(BOOKTABLE,
2193         $(TR $(TD DateTime) $(TD +) $(TD duration) $(TD -->) $(TD DateTime))
2194         $(TR $(TD DateTime) $(TD -) $(TD duration) $(TD -->) $(TD DateTime))
2195         )
2196
2197         Params:
2198             duration = The duration to add to or subtract from this
2199                        $(LREF DateTime).
2200       +/
2201     ref DateTime opOpAssign(string op, D)(in D duration) @safe pure nothrow @nogc
2202         if ((op == "+" || op == "-") &&
2203            (is(Unqual!D == Duration) ||
2204             is(Unqual!D == TickDuration)))
2205     {
2206         import std.format : format;
2207
2208         DateTime retval = this;
2209
2210         static if (is(Unqual!D == Duration))
2211             immutable hnsecs = duration.total!"hnsecs";
2212         else static if (is(Unqual!D == TickDuration))
2213             immutable hnsecs = duration.hnsecs;
2214
2215         mixin(format(`return _addSeconds(convert!("hnsecs", "seconds")(%shnsecs));`, op));
2216     }
2217
2218     @safe unittest
2219     {
2220         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"weeks"(7) ==
2221                DateTime(Date(1999, 8, 24), TimeOfDay(12, 30, 33)));
2222         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"weeks"(-7) ==
2223                DateTime(Date(1999, 5, 18), TimeOfDay(12, 30, 33)));
2224         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"days"(7) ==
2225                DateTime(Date(1999, 7, 13), TimeOfDay(12, 30, 33)));
2226         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"days"(-7) ==
2227                DateTime(Date(1999, 6, 29), TimeOfDay(12, 30, 33)));
2228
2229         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"hours"(7) ==
2230                DateTime(Date(1999, 7, 6), TimeOfDay(19, 30, 33)));
2231         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"hours"(-7) ==
2232                DateTime(Date(1999, 7, 6), TimeOfDay(5, 30, 33)));
2233         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"minutes"(7) ==
2234                DateTime(Date(1999, 7, 6), TimeOfDay(12, 37, 33)));
2235         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"minutes"(-7) ==
2236                DateTime(Date(1999, 7, 6), TimeOfDay(12, 23, 33)));
2237         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"seconds"(7) ==
2238                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2239         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"seconds"(-7) ==
2240                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2241         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"msecs"(7_000) ==
2242                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2243         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"msecs"(-7_000) ==
2244                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2245         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"usecs"(7_000_000) ==
2246                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2247         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"usecs"(-7_000_000) ==
2248                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2249         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"hnsecs"(70_000_000) ==
2250                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2251         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) + dur!"hnsecs"(-70_000_000) ==
2252                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2253
2254         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"weeks"(-7) ==
2255                DateTime(Date(1999, 8, 24), TimeOfDay(12, 30, 33)));
2256         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"weeks"(7) ==
2257                DateTime(Date(1999, 5, 18), TimeOfDay(12, 30, 33)));
2258         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"days"(-7) ==
2259                DateTime(Date(1999, 7, 13), TimeOfDay(12, 30, 33)));
2260         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"days"(7) ==
2261                DateTime(Date(1999, 6, 29), TimeOfDay(12, 30, 33)));
2262
2263         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"hours"(-7) ==
2264                DateTime(Date(1999, 7, 6), TimeOfDay(19, 30, 33)));
2265         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"hours"(7) ==
2266                DateTime(Date(1999, 7, 6), TimeOfDay(5, 30, 33)));
2267         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"minutes"(-7) ==
2268                DateTime(Date(1999, 7, 6), TimeOfDay(12, 37, 33)));
2269         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"minutes"(7) ==
2270                DateTime(Date(1999, 7, 6), TimeOfDay(12, 23, 33)));
2271         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"seconds"(-7) ==
2272                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2273         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"seconds"(7) ==
2274                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2275         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"msecs"(-7_000) ==
2276                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2277         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"msecs"(7_000) ==
2278                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2279         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"usecs"(-7_000_000) ==
2280                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2281         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"usecs"(7_000_000) ==
2282                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2283         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"hnsecs"(-70_000_000) ==
2284                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2285         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - dur!"hnsecs"(70_000_000) ==
2286                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2287
2288         auto dt = DateTime(2000, 1, 31, 9, 7, 6);
2289         (dt += dur!"seconds"(92)) -= dur!"days"(-500);
2290         assert(dt == DateTime(2001, 6, 14, 9, 8, 38));
2291
2292         auto duration = dur!"seconds"(12);
2293         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2294         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2295         static assert(!__traits(compiles, cdt += duration));
2296         static assert(!__traits(compiles, idt += duration));
2297         static assert(!__traits(compiles, cdt -= duration));
2298         static assert(!__traits(compiles, idt -= duration));
2299     }
2300
2301     // Explicitly undocumented. It will be removed in January 2018. @@@DEPRECATED_2018-01@@@
2302     deprecated("Use Duration instead of TickDuration.")
2303     ref DateTime opOpAssign(string op)(TickDuration td) @safe pure nothrow @nogc
2304         if (op == "+" || op == "-")
2305     {
2306         DateTime retval = this;
2307         immutable seconds = td.seconds;
2308         mixin("return _addSeconds(" ~ op ~ "seconds);");
2309     }
2310
2311     deprecated @safe unittest
2312     {
2313         // This probably only runs in cases where gettimeofday() is used, but it's
2314         // hard to do this test correctly with variable ticksPerSec.
2315         if (TickDuration.ticksPerSec == 1_000_000)
2316         {
2317             {
2318                 auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2319                 dt += TickDuration.from!"usecs"(7_000_000);
2320                 assert(dt == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2321             }
2322
2323             {
2324                 auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2325                 dt += TickDuration.from!"usecs"(-7_000_000);
2326                 assert(dt == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2327             }
2328
2329             {
2330                 auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2331                 dt -= TickDuration.from!"usecs"(-7_000_000);
2332                 assert(dt == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 40)));
2333             }
2334
2335             {
2336                 auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2337                 dt -= TickDuration.from!"usecs"(7_000_000);
2338                 assert(dt == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 26)));
2339             }
2340         }
2341     }
2342
2343
2344     /++
2345         Gives the difference between two $(LREF DateTime)s.
2346
2347         The legal types of arithmetic for $(LREF DateTime) using this operator are
2348
2349         $(BOOKTABLE,
2350         $(TR $(TD DateTime) $(TD -) $(TD DateTime) $(TD -->) $(TD duration))
2351         )
2352       +/
2353     Duration opBinary(string op)(in DateTime rhs) const @safe pure nothrow @nogc
2354         if (op == "-")
2355     {
2356         immutable dateResult = _date - rhs.date;
2357         immutable todResult = _tod - rhs._tod;
2358
2359         return dur!"hnsecs"(dateResult.total!"hnsecs" + todResult.total!"hnsecs");
2360     }
2361
2362     @safe unittest
2363     {
2364         auto dt = DateTime(1999, 7, 6, 12, 30, 33);
2365
2366         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1998, 7, 6), TimeOfDay(12, 30, 33)) ==
2367                dur!"seconds"(31_536_000));
2368         assert(DateTime(Date(1998, 7, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) ==
2369                dur!"seconds"(-31_536_000));
2370
2371         assert(DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) ==
2372                dur!"seconds"(26_78_400));
2373         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 8, 6), TimeOfDay(12, 30, 33)) ==
2374                dur!"seconds"(-26_78_400));
2375
2376         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 7, 5), TimeOfDay(12, 30, 33)) ==
2377                dur!"seconds"(86_400));
2378         assert(DateTime(Date(1999, 7, 5), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) ==
2379                dur!"seconds"(-86_400));
2380
2381         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(11, 30, 33)) ==
2382                dur!"seconds"(3600));
2383         assert(DateTime(Date(1999, 7, 6), TimeOfDay(11, 30, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) ==
2384                dur!"seconds"(-3600));
2385
2386         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) ==
2387                dur!"seconds"(60));
2388         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 31, 33)) ==
2389                dur!"seconds"(-60));
2390
2391         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) ==
2392                dur!"seconds"(1));
2393         assert(DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)) - DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 34)) ==
2394                dur!"seconds"(-1));
2395
2396         assert(DateTime(1, 1, 1, 12, 30, 33) - DateTime(1, 1, 1, 0, 0, 0) == dur!"seconds"(45033));
2397         assert(DateTime(1, 1, 1, 0, 0, 0) - DateTime(1, 1, 1, 12, 30, 33) == dur!"seconds"(-45033));
2398         assert(DateTime(0, 12, 31, 12, 30, 33) - DateTime(1, 1, 1, 0, 0, 0) == dur!"seconds"(-41367));
2399         assert(DateTime(1, 1, 1, 0, 0, 0) - DateTime(0, 12, 31, 12, 30, 33) == dur!"seconds"(41367));
2400
2401         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2402         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2403         assert(dt - dt == Duration.zero);
2404         assert(cdt - dt == Duration.zero);
2405         assert(idt - dt == Duration.zero);
2406
2407         assert(dt - cdt == Duration.zero);
2408         assert(cdt - cdt == Duration.zero);
2409         assert(idt - cdt == Duration.zero);
2410
2411         assert(dt - idt == Duration.zero);
2412         assert(cdt - idt == Duration.zero);
2413         assert(idt - idt == Duration.zero);
2414     }
2415
2416
2417     /++
2418         Returns the difference between the two $(LREF DateTime)s in months.
2419
2420         To get the difference in years, subtract the year property
2421         of two $(LREF DateTime)s. To get the difference in days or weeks,
2422         subtract the $(LREF DateTime)s themselves and use the
2423         $(REF Duration, core,time) that results. Because converting between
2424         months and smaller units requires a specific date (which
2425         $(REF Duration, core,time)s don't have), getting the difference in
2426         months requires some math using both the year and month properties, so
2427         this is a convenience function for getting the difference in months.
2428
2429         Note that the number of days in the months or how far into the month
2430         either date is is irrelevant. It is the difference in the month property
2431         combined with the difference in years * 12. So, for instance,
2432         December 31st and January 1st are one month apart just as December 1st
2433         and January 31st are one month apart.
2434
2435         Params:
2436             rhs = The $(LREF DateTime) to subtract from this one.
2437       +/
2438     int diffMonths(in DateTime rhs) const @safe pure nothrow @nogc
2439     {
2440         return _date.diffMonths(rhs._date);
2441     }
2442
2443     ///
2444     @safe unittest
2445     {
2446         assert(DateTime(1999, 2, 1, 12, 2, 3).diffMonths(
2447                    DateTime(1999, 1, 31, 23, 59, 59)) == 1);
2448
2449         assert(DateTime(1999, 1, 31, 0, 0, 0).diffMonths(
2450                    DateTime(1999, 2, 1, 12, 3, 42)) == -1);
2451
2452         assert(DateTime(1999, 3, 1, 5, 30, 0).diffMonths(
2453                    DateTime(1999, 1, 1, 2, 4, 7)) == 2);
2454
2455         assert(DateTime(1999, 1, 1, 7, 2, 4).diffMonths(
2456                    DateTime(1999, 3, 31, 0, 30, 58)) == -2);
2457     }
2458
2459     @safe unittest
2460     {
2461         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2462         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2463         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2464         assert(dt.diffMonths(dt) == 0);
2465         assert(cdt.diffMonths(dt) == 0);
2466         assert(idt.diffMonths(dt) == 0);
2467
2468         assert(dt.diffMonths(cdt) == 0);
2469         assert(cdt.diffMonths(cdt) == 0);
2470         assert(idt.diffMonths(cdt) == 0);
2471
2472         assert(dt.diffMonths(idt) == 0);
2473         assert(cdt.diffMonths(idt) == 0);
2474         assert(idt.diffMonths(idt) == 0);
2475     }
2476
2477
2478     /++
2479         Whether this $(LREF DateTime) is in a leap year.
2480      +/
2481     @property bool isLeapYear() const @safe pure nothrow @nogc
2482     {
2483         return _date.isLeapYear;
2484     }
2485
2486     @safe unittest
2487     {
2488         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2489         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2490         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2491         assert(!dt.isLeapYear);
2492         assert(!cdt.isLeapYear);
2493         assert(!idt.isLeapYear);
2494     }
2495
2496
2497     /++
2498         Day of the week this $(LREF DateTime) is on.
2499       +/
2500     @property DayOfWeek dayOfWeek() const @safe pure nothrow @nogc
2501     {
2502         return _date.dayOfWeek;
2503     }
2504
2505     @safe unittest
2506     {
2507         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2508         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2509         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2510         assert(dt.dayOfWeek == DayOfWeek.tue);
2511         assert(cdt.dayOfWeek == DayOfWeek.tue);
2512         assert(idt.dayOfWeek == DayOfWeek.tue);
2513     }
2514
2515
2516     /++
2517         Day of the year this $(LREF DateTime) is on.
2518       +/
2519     @property ushort dayOfYear() const @safe pure nothrow @nogc
2520     {
2521         return _date.dayOfYear;
2522     }
2523
2524     ///
2525     @safe unittest
2526     {
2527         assert(DateTime(Date(1999, 1, 1), TimeOfDay(12, 22, 7)).dayOfYear == 1);
2528         assert(DateTime(Date(1999, 12, 31), TimeOfDay(7, 2, 59)).dayOfYear == 365);
2529         assert(DateTime(Date(2000, 12, 31), TimeOfDay(21, 20, 0)).dayOfYear == 366);
2530     }
2531
2532     @safe unittest
2533     {
2534         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2535         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2536         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2537         assert(dt.dayOfYear == 187);
2538         assert(cdt.dayOfYear == 187);
2539         assert(idt.dayOfYear == 187);
2540     }
2541
2542
2543     /++
2544         Day of the year.
2545
2546         Params:
2547             day = The day of the year to set which day of the year this
2548                   $(LREF DateTime) is on.
2549       +/
2550     @property void dayOfYear(int day) @safe pure
2551     {
2552         _date.dayOfYear = day;
2553     }
2554
2555     @safe unittest
2556     {
2557         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2558         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2559         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2560         dt.dayOfYear = 12;
2561         assert(dt.dayOfYear == 12);
2562         static assert(!__traits(compiles, cdt.dayOfYear = 12));
2563         static assert(!__traits(compiles, idt.dayOfYear = 12));
2564     }
2565
2566
2567     /++
2568         The Xth day of the Gregorian Calendar that this $(LREF DateTime) is on.
2569      +/
2570     @property int dayOfGregorianCal() const @safe pure nothrow @nogc
2571     {
2572         return _date.dayOfGregorianCal;
2573     }
2574
2575     ///
2576     @safe unittest
2577     {
2578         assert(DateTime(Date(1, 1, 1), TimeOfDay(0, 0, 0)).dayOfGregorianCal == 1);
2579         assert(DateTime(Date(1, 12, 31), TimeOfDay(23, 59, 59)).dayOfGregorianCal == 365);
2580         assert(DateTime(Date(2, 1, 1), TimeOfDay(2, 2, 2)).dayOfGregorianCal == 366);
2581
2582         assert(DateTime(Date(0, 12, 31), TimeOfDay(7, 7, 7)).dayOfGregorianCal == 0);
2583         assert(DateTime(Date(0, 1, 1), TimeOfDay(19, 30, 0)).dayOfGregorianCal == -365);
2584         assert(DateTime(Date(-1, 12, 31), TimeOfDay(4, 7, 0)).dayOfGregorianCal == -366);
2585
2586         assert(DateTime(Date(2000, 1, 1), TimeOfDay(9, 30, 20)).dayOfGregorianCal == 730_120);
2587         assert(DateTime(Date(2010, 12, 31), TimeOfDay(15, 45, 50)).dayOfGregorianCal == 734_137);
2588     }
2589
2590     @safe unittest
2591     {
2592         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2593         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2594         assert(cdt.dayOfGregorianCal == 729_941);
2595         assert(idt.dayOfGregorianCal == 729_941);
2596     }
2597
2598
2599     /++
2600         The Xth day of the Gregorian Calendar that this $(LREF DateTime) is on.
2601         Setting this property does not affect the time portion of
2602         $(LREF DateTime).
2603
2604         Params:
2605             days = The day of the Gregorian Calendar to set this $(LREF DateTime)
2606                    to.
2607      +/
2608     @property void dayOfGregorianCal(int days) @safe pure nothrow @nogc
2609     {
2610         _date.dayOfGregorianCal = days;
2611     }
2612
2613     ///
2614     @safe unittest
2615     {
2616         auto dt = DateTime(Date.init, TimeOfDay(12, 0, 0));
2617         dt.dayOfGregorianCal = 1;
2618         assert(dt == DateTime(Date(1, 1, 1), TimeOfDay(12, 0, 0)));
2619
2620         dt.dayOfGregorianCal = 365;
2621         assert(dt == DateTime(Date(1, 12, 31), TimeOfDay(12, 0, 0)));
2622
2623         dt.dayOfGregorianCal = 366;
2624         assert(dt == DateTime(Date(2, 1, 1), TimeOfDay(12, 0, 0)));
2625
2626         dt.dayOfGregorianCal = 0;
2627         assert(dt == DateTime(Date(0, 12, 31), TimeOfDay(12, 0, 0)));
2628
2629         dt.dayOfGregorianCal = -365;
2630         assert(dt == DateTime(Date(-0, 1, 1), TimeOfDay(12, 0, 0)));
2631
2632         dt.dayOfGregorianCal = -366;
2633         assert(dt == DateTime(Date(-1, 12, 31), TimeOfDay(12, 0, 0)));
2634
2635         dt.dayOfGregorianCal = 730_120;
2636         assert(dt == DateTime(Date(2000, 1, 1), TimeOfDay(12, 0, 0)));
2637
2638         dt.dayOfGregorianCal = 734_137;
2639         assert(dt == DateTime(Date(2010, 12, 31), TimeOfDay(12, 0, 0)));
2640     }
2641
2642     @safe unittest
2643     {
2644         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2645         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2646         static assert(!__traits(compiles, cdt.dayOfGregorianCal = 7));
2647         static assert(!__traits(compiles, idt.dayOfGregorianCal = 7));
2648     }
2649
2650
2651     /++
2652         The ISO 8601 week of the year that this $(LREF DateTime) is in.
2653
2654         See_Also:
2655             $(HTTP en.wikipedia.org/wiki/ISO_week_date, ISO Week Date)
2656       +/
2657     @property ubyte isoWeek() const @safe pure nothrow
2658     {
2659         return _date.isoWeek;
2660     }
2661
2662     @safe unittest
2663     {
2664         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2665         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2666         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2667         assert(dt.isoWeek == 27);
2668         assert(cdt.isoWeek == 27);
2669         assert(idt.isoWeek == 27);
2670     }
2671
2672
2673     /++
2674         $(LREF DateTime) for the last day in the month that this
2675         $(LREF DateTime) is in. The time portion of endOfMonth is always
2676         23:59:59.
2677       +/
2678     @property DateTime endOfMonth() const @safe pure nothrow
2679     {
2680         try
2681             return DateTime(_date.endOfMonth, TimeOfDay(23, 59, 59));
2682         catch (Exception e)
2683             assert(0, "DateTime constructor threw.");
2684     }
2685
2686     ///
2687     @safe unittest
2688     {
2689         assert(DateTime(Date(1999, 1, 6), TimeOfDay(0, 0, 0)).endOfMonth ==
2690                DateTime(Date(1999, 1, 31), TimeOfDay(23, 59, 59)));
2691
2692         assert(DateTime(Date(1999, 2, 7), TimeOfDay(19, 30, 0)).endOfMonth ==
2693                DateTime(Date(1999, 2, 28), TimeOfDay(23, 59, 59)));
2694
2695         assert(DateTime(Date(2000, 2, 7), TimeOfDay(5, 12, 27)).endOfMonth ==
2696                DateTime(Date(2000, 2, 29), TimeOfDay(23, 59, 59)));
2697
2698         assert(DateTime(Date(2000, 6, 4), TimeOfDay(12, 22, 9)).endOfMonth ==
2699                DateTime(Date(2000, 6, 30), TimeOfDay(23, 59, 59)));
2700     }
2701
2702     @safe unittest
2703     {
2704         // Test A.D.
2705         assert(DateTime(1999, 1, 1, 0, 13, 26).endOfMonth == DateTime(1999, 1, 31, 23, 59, 59));
2706         assert(DateTime(1999, 2, 1, 1, 14, 27).endOfMonth == DateTime(1999, 2, 28, 23, 59, 59));
2707         assert(DateTime(2000, 2, 1, 2, 15, 28).endOfMonth == DateTime(2000, 2, 29, 23, 59, 59));
2708         assert(DateTime(1999, 3, 1, 3, 16, 29).endOfMonth == DateTime(1999, 3, 31, 23, 59, 59));
2709         assert(DateTime(1999, 4, 1, 4, 17, 30).endOfMonth == DateTime(1999, 4, 30, 23, 59, 59));
2710         assert(DateTime(1999, 5, 1, 5, 18, 31).endOfMonth == DateTime(1999, 5, 31, 23, 59, 59));
2711         assert(DateTime(1999, 6, 1, 6, 19, 32).endOfMonth == DateTime(1999, 6, 30, 23, 59, 59));
2712         assert(DateTime(1999, 7, 1, 7, 20, 33).endOfMonth == DateTime(1999, 7, 31, 23, 59, 59));
2713         assert(DateTime(1999, 8, 1, 8, 21, 34).endOfMonth == DateTime(1999, 8, 31, 23, 59, 59));
2714         assert(DateTime(1999, 9, 1, 9, 22, 35).endOfMonth == DateTime(1999, 9, 30, 23, 59, 59));
2715         assert(DateTime(1999, 10, 1, 10, 23, 36).endOfMonth == DateTime(1999, 10, 31, 23, 59, 59));
2716         assert(DateTime(1999, 11, 1, 11, 24, 37).endOfMonth == DateTime(1999, 11, 30, 23, 59, 59));
2717         assert(DateTime(1999, 12, 1, 12, 25, 38).endOfMonth == DateTime(1999, 12, 31, 23, 59, 59));
2718
2719         // Test B.C.
2720         assert(DateTime(-1999, 1, 1, 0, 13, 26).endOfMonth == DateTime(-1999, 1, 31, 23, 59, 59));
2721         assert(DateTime(-1999, 2, 1, 1, 14, 27).endOfMonth == DateTime(-1999, 2, 28, 23, 59, 59));
2722         assert(DateTime(-2000, 2, 1, 2, 15, 28).endOfMonth == DateTime(-2000, 2, 29, 23, 59, 59));
2723         assert(DateTime(-1999, 3, 1, 3, 16, 29).endOfMonth == DateTime(-1999, 3, 31, 23, 59, 59));
2724         assert(DateTime(-1999, 4, 1, 4, 17, 30).endOfMonth == DateTime(-1999, 4, 30, 23, 59, 59));
2725         assert(DateTime(-1999, 5, 1, 5, 18, 31).endOfMonth == DateTime(-1999, 5, 31, 23, 59, 59));
2726         assert(DateTime(-1999, 6, 1, 6, 19, 32).endOfMonth == DateTime(-1999, 6, 30, 23, 59, 59));
2727         assert(DateTime(-1999, 7, 1, 7, 20, 33).endOfMonth == DateTime(-1999, 7, 31, 23, 59, 59));
2728         assert(DateTime(-1999, 8, 1, 8, 21, 34).endOfMonth == DateTime(-1999, 8, 31, 23, 59, 59));
2729         assert(DateTime(-1999, 9, 1, 9, 22, 35).endOfMonth == DateTime(-1999, 9, 30, 23, 59, 59));
2730         assert(DateTime(-1999, 10, 1, 10, 23, 36).endOfMonth == DateTime(-1999, 10, 31, 23, 59, 59));
2731         assert(DateTime(-1999, 11, 1, 11, 24, 37).endOfMonth == DateTime(-1999, 11, 30, 23, 59, 59));
2732         assert(DateTime(-1999, 12, 1, 12, 25, 38).endOfMonth == DateTime(-1999, 12, 31, 23, 59, 59));
2733
2734         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2735         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2736         assert(cdt.endOfMonth == DateTime(1999, 7, 31, 23, 59, 59));
2737         assert(idt.endOfMonth == DateTime(1999, 7, 31, 23, 59, 59));
2738     }
2739
2740
2741     /++
2742         The last day in the month that this $(LREF DateTime) is in.
2743       +/
2744     @property ubyte daysInMonth() const @safe pure nothrow @nogc
2745     {
2746         return _date.daysInMonth;
2747     }
2748
2749     ///
2750     @safe unittest
2751     {
2752         assert(DateTime(Date(1999, 1, 6), TimeOfDay(0, 0, 0)).daysInMonth == 31);
2753         assert(DateTime(Date(1999, 2, 7), TimeOfDay(19, 30, 0)).daysInMonth == 28);
2754         assert(DateTime(Date(2000, 2, 7), TimeOfDay(5, 12, 27)).daysInMonth == 29);
2755         assert(DateTime(Date(2000, 6, 4), TimeOfDay(12, 22, 9)).daysInMonth == 30);
2756     }
2757
2758     @safe unittest
2759     {
2760         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2761         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2762         assert(cdt.daysInMonth == 31);
2763         assert(idt.daysInMonth == 31);
2764     }
2765
2766
2767     /++
2768         Whether the current year is a date in A.D.
2769       +/
2770     @property bool isAD() const @safe pure nothrow @nogc
2771     {
2772         return _date.isAD;
2773     }
2774
2775     ///
2776     @safe unittest
2777     {
2778         assert(DateTime(Date(1, 1, 1), TimeOfDay(12, 7, 0)).isAD);
2779         assert(DateTime(Date(2010, 12, 31), TimeOfDay(0, 0, 0)).isAD);
2780         assert(!DateTime(Date(0, 12, 31), TimeOfDay(23, 59, 59)).isAD);
2781         assert(!DateTime(Date(-2010, 1, 1), TimeOfDay(2, 2, 2)).isAD);
2782     }
2783
2784     @safe unittest
2785     {
2786         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2787         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2788         assert(cdt.isAD);
2789         assert(idt.isAD);
2790     }
2791
2792
2793     /++
2794         The $(HTTP en.wikipedia.org/wiki/Julian_day, Julian day) for this
2795         $(LREF DateTime) at the given time. For example, prior to noon,
2796         1996-03-31 would be the Julian day number 2_450_173, so this function
2797         returns 2_450_173, while from noon onward, the julian day number would
2798         be 2_450_174, so this function returns 2_450_174.
2799       +/
2800     @property long julianDay() const @safe pure nothrow @nogc
2801     {
2802         if (_tod._hour < 12)
2803             return _date.julianDay - 1;
2804         else
2805             return _date.julianDay;
2806     }
2807
2808     @safe unittest
2809     {
2810         assert(DateTime(Date(-4713, 11, 24), TimeOfDay(0, 0, 0)).julianDay == -1);
2811         assert(DateTime(Date(-4713, 11, 24), TimeOfDay(12, 0, 0)).julianDay == 0);
2812
2813         assert(DateTime(Date(0, 12, 31), TimeOfDay(0, 0, 0)).julianDay == 1_721_424);
2814         assert(DateTime(Date(0, 12, 31), TimeOfDay(12, 0, 0)).julianDay == 1_721_425);
2815
2816         assert(DateTime(Date(1, 1, 1), TimeOfDay(0, 0, 0)).julianDay == 1_721_425);
2817         assert(DateTime(Date(1, 1, 1), TimeOfDay(12, 0, 0)).julianDay == 1_721_426);
2818
2819         assert(DateTime(Date(1582, 10, 15), TimeOfDay(0, 0, 0)).julianDay == 2_299_160);
2820         assert(DateTime(Date(1582, 10, 15), TimeOfDay(12, 0, 0)).julianDay == 2_299_161);
2821
2822         assert(DateTime(Date(1858, 11, 17), TimeOfDay(0, 0, 0)).julianDay == 2_400_000);
2823         assert(DateTime(Date(1858, 11, 17), TimeOfDay(12, 0, 0)).julianDay == 2_400_001);
2824
2825         assert(DateTime(Date(1982, 1, 4), TimeOfDay(0, 0, 0)).julianDay == 2_444_973);
2826         assert(DateTime(Date(1982, 1, 4), TimeOfDay(12, 0, 0)).julianDay == 2_444_974);
2827
2828         assert(DateTime(Date(1996, 3, 31), TimeOfDay(0, 0, 0)).julianDay == 2_450_173);
2829         assert(DateTime(Date(1996, 3, 31), TimeOfDay(12, 0, 0)).julianDay == 2_450_174);
2830
2831         assert(DateTime(Date(2010, 8, 24), TimeOfDay(0, 0, 0)).julianDay == 2_455_432);
2832         assert(DateTime(Date(2010, 8, 24), TimeOfDay(12, 0, 0)).julianDay == 2_455_433);
2833
2834         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2835         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2836         assert(cdt.julianDay == 2_451_366);
2837         assert(idt.julianDay == 2_451_366);
2838     }
2839
2840
2841     /++
2842         The modified $(HTTP en.wikipedia.org/wiki/Julian_day, Julian day) for any
2843         time on this date (since, the modified Julian day changes at midnight).
2844       +/
2845     @property long modJulianDay() const @safe pure nothrow @nogc
2846     {
2847         return _date.modJulianDay;
2848     }
2849
2850     @safe unittest
2851     {
2852         assert(DateTime(Date(1858, 11, 17), TimeOfDay(0, 0, 0)).modJulianDay == 0);
2853         assert(DateTime(Date(1858, 11, 17), TimeOfDay(12, 0, 0)).modJulianDay == 0);
2854
2855         assert(DateTime(Date(2010, 8, 24), TimeOfDay(0, 0, 0)).modJulianDay == 55_432);
2856         assert(DateTime(Date(2010, 8, 24), TimeOfDay(12, 0, 0)).modJulianDay == 55_432);
2857
2858         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2859         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
2860         assert(cdt.modJulianDay == 51_365);
2861         assert(idt.modJulianDay == 51_365);
2862     }
2863
2864
2865     /++
2866         Converts this $(LREF DateTime) to a string with the format YYYYMMDDTHHMMSS.
2867       +/
2868     string toISOString() const @safe pure nothrow
2869     {
2870         import std.format : format;
2871         try
2872         {
2873             return format!("%sT%02d%02d%02d")(
2874                 _date.toISOString(),
2875                 _tod._hour,
2876                 _tod._minute,
2877                 _tod._second
2878             );
2879         }
2880         catch (Exception e)
2881         {
2882             assert(0, "format() threw.");
2883         }
2884     }
2885
2886     ///
2887     @safe unittest
2888     {
2889         assert(DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)).toISOString() ==
2890                "20100704T070612");
2891
2892         assert(DateTime(Date(1998, 12, 25), TimeOfDay(2, 15, 0)).toISOString() ==
2893                "19981225T021500");
2894
2895         assert(DateTime(Date(0, 1, 5), TimeOfDay(23, 9, 59)).toISOString() ==
2896                "00000105T230959");
2897
2898         assert(DateTime(Date(-4, 1, 5), TimeOfDay(0, 0, 2)).toISOString() ==
2899                "-00040105T000002");
2900     }
2901
2902     @safe unittest
2903     {
2904         // Test A.D.
2905         assert(DateTime(Date(9, 12, 4), TimeOfDay(0, 0, 0)).toISOString() == "00091204T000000");
2906         assert(DateTime(Date(99, 12, 4), TimeOfDay(5, 6, 12)).toISOString() == "00991204T050612");
2907         assert(DateTime(Date(999, 12, 4), TimeOfDay(13, 44, 59)).toISOString() == "09991204T134459");
2908         assert(DateTime(Date(9999, 7, 4), TimeOfDay(23, 59, 59)).toISOString() == "99990704T235959");
2909         assert(DateTime(Date(10000, 10, 20), TimeOfDay(1, 1, 1)).toISOString() == "+100001020T010101");
2910
2911         // Test B.C.
2912         assert(DateTime(Date(0, 12, 4), TimeOfDay(0, 12, 4)).toISOString() == "00001204T001204");
2913         assert(DateTime(Date(-9, 12, 4), TimeOfDay(0, 0, 0)).toISOString() == "-00091204T000000");
2914         assert(DateTime(Date(-99, 12, 4), TimeOfDay(5, 6, 12)).toISOString() == "-00991204T050612");
2915         assert(DateTime(Date(-999, 12, 4), TimeOfDay(13, 44, 59)).toISOString() == "-09991204T134459");
2916         assert(DateTime(Date(-9999, 7, 4), TimeOfDay(23, 59, 59)).toISOString() == "-99990704T235959");
2917         assert(DateTime(Date(-10000, 10, 20), TimeOfDay(1, 1, 1)).toISOString() == "-100001020T010101");
2918
2919         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
2920         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
2921         assert(cdt.toISOString() == "19990706T123033");
2922         assert(idt.toISOString() == "19990706T123033");
2923     }
2924
2925
2926     /++
2927         Converts this $(LREF DateTime) to a string with the format
2928         YYYY-MM-DDTHH:MM:SS.
2929       +/
2930     string toISOExtString() const @safe pure nothrow
2931     {
2932         import std.format : format;
2933         try
2934         {
2935             return format!("%sT%02d:%02d:%02d")(
2936                 _date.toISOExtString(),
2937                 _tod._hour,
2938                 _tod._minute,
2939                 _tod._second
2940             );
2941         }
2942         catch (Exception e)
2943         {
2944             assert(0, "format() threw.");
2945         }
2946     }
2947
2948     ///
2949     @safe unittest
2950     {
2951         assert(DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)).toISOExtString() ==
2952                "2010-07-04T07:06:12");
2953
2954         assert(DateTime(Date(1998, 12, 25), TimeOfDay(2, 15, 0)).toISOExtString() ==
2955                "1998-12-25T02:15:00");
2956
2957         assert(DateTime(Date(0, 1, 5), TimeOfDay(23, 9, 59)).toISOExtString() ==
2958                "0000-01-05T23:09:59");
2959
2960         assert(DateTime(Date(-4, 1, 5), TimeOfDay(0, 0, 2)).toISOExtString() ==
2961                "-0004-01-05T00:00:02");
2962     }
2963
2964     @safe unittest
2965     {
2966         // Test A.D.
2967         assert(DateTime(Date(9, 12, 4), TimeOfDay(0, 0, 0)).toISOExtString() == "0009-12-04T00:00:00");
2968         assert(DateTime(Date(99, 12, 4), TimeOfDay(5, 6, 12)).toISOExtString() == "0099-12-04T05:06:12");
2969         assert(DateTime(Date(999, 12, 4), TimeOfDay(13, 44, 59)).toISOExtString() == "0999-12-04T13:44:59");
2970         assert(DateTime(Date(9999, 7, 4), TimeOfDay(23, 59, 59)).toISOExtString() == "9999-07-04T23:59:59");
2971         assert(DateTime(Date(10000, 10, 20), TimeOfDay(1, 1, 1)).toISOExtString() == "+10000-10-20T01:01:01");
2972
2973         // Test B.C.
2974         assert(DateTime(Date(0, 12, 4), TimeOfDay(0, 12, 4)).toISOExtString() == "0000-12-04T00:12:04");
2975         assert(DateTime(Date(-9, 12, 4), TimeOfDay(0, 0, 0)).toISOExtString() == "-0009-12-04T00:00:00");
2976         assert(DateTime(Date(-99, 12, 4), TimeOfDay(5, 6, 12)).toISOExtString() == "-0099-12-04T05:06:12");
2977         assert(DateTime(Date(-999, 12, 4), TimeOfDay(13, 44, 59)).toISOExtString() == "-0999-12-04T13:44:59");
2978         assert(DateTime(Date(-9999, 7, 4), TimeOfDay(23, 59, 59)).toISOExtString() == "-9999-07-04T23:59:59");
2979         assert(DateTime(Date(-10000, 10, 20), TimeOfDay(1, 1, 1)).toISOExtString() == "-10000-10-20T01:01:01");
2980
2981         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
2982         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
2983         assert(cdt.toISOExtString() == "1999-07-06T12:30:33");
2984         assert(idt.toISOExtString() == "1999-07-06T12:30:33");
2985     }
2986
2987     /++
2988         Converts this $(LREF DateTime) to a string with the format
2989         YYYY-Mon-DD HH:MM:SS.
2990       +/
2991     string toSimpleString() const @safe pure nothrow
2992     {
2993         import std.format : format;
2994         try
2995         {
2996             return format!("%s %02d:%02d:%02d")(
2997                 _date.toSimpleString(),
2998                 _tod._hour,
2999                 _tod._minute,
3000                 _tod._second
3001             );
3002         }
3003         catch (Exception e)
3004         {
3005             assert(0, "format() threw.");
3006         }
3007     }
3008
3009     ///
3010     @safe unittest
3011     {
3012         assert(DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)).toSimpleString() ==
3013                "2010-Jul-04 07:06:12");
3014
3015         assert(DateTime(Date(1998, 12, 25), TimeOfDay(2, 15, 0)).toSimpleString() ==
3016                "1998-Dec-25 02:15:00");
3017
3018         assert(DateTime(Date(0, 1, 5), TimeOfDay(23, 9, 59)).toSimpleString() ==
3019                "0000-Jan-05 23:09:59");
3020
3021         assert(DateTime(Date(-4, 1, 5), TimeOfDay(0, 0, 2)).toSimpleString() ==
3022                "-0004-Jan-05 00:00:02");
3023     }
3024
3025     @safe unittest
3026     {
3027         // Test A.D.
3028         assert(DateTime(Date(9, 12, 4), TimeOfDay(0, 0, 0)).toSimpleString() == "0009-Dec-04 00:00:00");
3029         assert(DateTime(Date(99, 12, 4), TimeOfDay(5, 6, 12)).toSimpleString() == "0099-Dec-04 05:06:12");
3030         assert(DateTime(Date(999, 12, 4), TimeOfDay(13, 44, 59)).toSimpleString() == "0999-Dec-04 13:44:59");
3031         assert(DateTime(Date(9999, 7, 4), TimeOfDay(23, 59, 59)).toSimpleString() == "9999-Jul-04 23:59:59");
3032         assert(DateTime(Date(10000, 10, 20), TimeOfDay(1, 1, 1)).toSimpleString() == "+10000-Oct-20 01:01:01");
3033
3034         // Test B.C.
3035         assert(DateTime(Date(0, 12, 4), TimeOfDay(0, 12, 4)).toSimpleString() == "0000-Dec-04 00:12:04");
3036         assert(DateTime(Date(-9, 12, 4), TimeOfDay(0, 0, 0)).toSimpleString() == "-0009-Dec-04 00:00:00");
3037         assert(DateTime(Date(-99, 12, 4), TimeOfDay(5, 6, 12)).toSimpleString() == "-0099-Dec-04 05:06:12");
3038         assert(DateTime(Date(-999, 12, 4), TimeOfDay(13, 44, 59)).toSimpleString() == "-0999-Dec-04 13:44:59");
3039         assert(DateTime(Date(-9999, 7, 4), TimeOfDay(23, 59, 59)).toSimpleString() == "-9999-Jul-04 23:59:59");
3040         assert(DateTime(Date(-10000, 10, 20), TimeOfDay(1, 1, 1)).toSimpleString() == "-10000-Oct-20 01:01:01");
3041
3042         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
3043         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
3044         assert(cdt.toSimpleString() == "1999-Jul-06 12:30:33");
3045         assert(idt.toSimpleString() == "1999-Jul-06 12:30:33");
3046     }
3047
3048
3049     /++
3050         Converts this $(LREF DateTime) to a string.
3051
3052         This function exists to make it easy to convert a $(LREF DateTime) to a
3053         string for code that does not care what the exact format is - just that
3054         it presents the information in a clear manner. It also makes it easy to
3055         simply convert a $(LREF DateTime) to a string when using functions such
3056         as `to!string`, `format`, or `writeln` which use toString to convert
3057         user-defined types. So, it is unlikely that much code will call
3058         toString directly.
3059
3060         The format of the string is purposefully unspecified, and code that
3061         cares about the format of the string should use `toISOString`,
3062         `toISOExtString`, `toSimpleString`, or some other custom formatting
3063         function that explicitly generates the format that the code needs. The
3064         reason is that the code is then clear about what format it's using,
3065         making it less error-prone to maintain the code and interact with other
3066         software that consumes the generated strings. It's for this same reason
3067         that $(LREF DateTime) has no `fromString` function, whereas it does have
3068         `fromISOString`, `fromISOExtString`, and `fromSimpleString`.
3069
3070         The format returned by toString may or may not change in the future.
3071       +/
3072     string toString() const @safe pure nothrow
3073     {
3074         return toSimpleString();
3075     }
3076
3077     @safe unittest
3078     {
3079         auto dt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
3080         const cdt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
3081         immutable idt = DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33));
3082         assert(dt.toString());
3083         assert(cdt.toString());
3084         assert(idt.toString());
3085     }
3086
3087
3088
3089     /++
3090         Creates a $(LREF DateTime) from a string with the format YYYYMMDDTHHMMSS.
3091         Whitespace is stripped from the given string.
3092
3093         Params:
3094             isoString = A string formatted in the ISO format for dates and times.
3095
3096         Throws:
3097             $(REF DateTimeException,std,datetime,date) if the given string is
3098             not in the ISO format or if the resulting $(LREF DateTime) would not
3099             be valid.
3100       +/
3101     static DateTime fromISOString(S)(in S isoString) @safe pure
3102         if (isSomeString!S)
3103     {
3104         import std.algorithm.searching : countUntil;
3105         import std.exception : enforce;
3106         import std.format : format;
3107         import std.string : strip;
3108
3109         auto str = strip(isoString);
3110
3111         enforce(str.length >= 15, new DateTimeException(format("Invalid ISO String: %s", isoString)));
3112         auto t = str.countUntil('T');
3113
3114         enforce(t != -1, new DateTimeException(format("Invalid ISO String: %s", isoString)));
3115
3116         immutable date = Date.fromISOString(str[0 .. t]);
3117         immutable tod = TimeOfDay.fromISOString(str[t+1 .. $]);
3118
3119         return DateTime(date, tod);
3120     }
3121
3122     ///
3123     @safe unittest
3124     {
3125         assert(DateTime.fromISOString("20100704T070612") ==
3126                DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)));
3127
3128         assert(DateTime.fromISOString("19981225T021500") ==
3129                DateTime(Date(1998, 12, 25), TimeOfDay(2, 15, 0)));
3130
3131         assert(DateTime.fromISOString("00000105T230959") ==
3132                DateTime(Date(0, 1, 5), TimeOfDay(23, 9, 59)));
3133
3134         assert(DateTime.fromISOString("-00040105T000002") ==
3135                DateTime(Date(-4, 1, 5), TimeOfDay(0, 0, 2)));
3136
3137         assert(DateTime.fromISOString(" 20100704T070612 ") ==
3138                DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)));
3139     }
3140
3141     @safe unittest
3142     {
3143         assertThrown!DateTimeException(DateTime.fromISOString(""));
3144         assertThrown!DateTimeException(DateTime.fromISOString("20100704000000"));
3145         assertThrown!DateTimeException(DateTime.fromISOString("20100704 000000"));
3146         assertThrown!DateTimeException(DateTime.fromISOString("20100704t000000"));
3147         assertThrown!DateTimeException(DateTime.fromISOString("20100704T000000."));
3148         assertThrown!DateTimeException(DateTime.fromISOString("20100704T000000.0"));
3149
3150         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-0400:00:00"));
3151         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04 00:00:00"));
3152         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04t00:00:00"));
3153         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04T00:00:00."));
3154         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04T00:00:00.0"));
3155
3156         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-0400:00:00"));
3157         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04 00:00:00"));
3158         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04t00:00:00"));
3159         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04T00:00:00"));
3160         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04 00:00:00."));
3161         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04 00:00:00.0"));
3162
3163         assertThrown!DateTimeException(DateTime.fromISOString("2010-12-22T172201"));
3164         assertThrown!DateTimeException(DateTime.fromISOString("2010-Dec-22 17:22:01"));
3165
3166         assert(DateTime.fromISOString("20101222T172201") == DateTime(Date(2010, 12, 22), TimeOfDay(17, 22, 01)));
3167         assert(DateTime.fromISOString("19990706T123033") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3168         assert(DateTime.fromISOString("-19990706T123033") == DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
3169         assert(DateTime.fromISOString("+019990706T123033") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3170         assert(DateTime.fromISOString("19990706T123033 ") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3171         assert(DateTime.fromISOString(" 19990706T123033") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3172         assert(DateTime.fromISOString(" 19990706T123033 ") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3173     }
3174
3175     // bug# 17801
3176     @safe unittest
3177     {
3178         import std.conv : to;
3179         import std.meta : AliasSeq;
3180         foreach (C; AliasSeq!(char, wchar, dchar))
3181         {
3182             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
3183                 assert(DateTime.fromISOString(to!S("20121221T141516")) == DateTime(2012, 12, 21, 14, 15, 16));
3184         }
3185     }
3186
3187
3188     /++
3189         Creates a $(LREF DateTime) from a string with the format
3190         YYYY-MM-DDTHH:MM:SS. Whitespace is stripped from the given string.
3191
3192         Params:
3193             isoExtString = A string formatted in the ISO Extended format for dates
3194                            and times.
3195
3196         Throws:
3197             $(REF DateTimeException,std,datetime,date) if the given string is
3198             not in the ISO Extended format or if the resulting $(LREF DateTime)
3199             would not be valid.
3200       +/
3201     static DateTime fromISOExtString(S)(in S isoExtString) @safe pure
3202         if (isSomeString!(S))
3203     {
3204         import std.algorithm.searching : countUntil;
3205         import std.exception : enforce;
3206         import std.format : format;
3207         import std.string : strip;
3208
3209         auto str = strip(isoExtString);
3210
3211         enforce(str.length >= 15, new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
3212         auto t = str.countUntil('T');
3213
3214         enforce(t != -1, new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
3215
3216         immutable date = Date.fromISOExtString(str[0 .. t]);
3217         immutable tod = TimeOfDay.fromISOExtString(str[t+1 .. $]);
3218
3219         return DateTime(date, tod);
3220     }
3221
3222     ///
3223     @safe unittest
3224     {
3225         assert(DateTime.fromISOExtString("2010-07-04T07:06:12") ==
3226                DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)));
3227
3228         assert(DateTime.fromISOExtString("1998-12-25T02:15:00") ==
3229                DateTime(Date(1998, 12, 25), TimeOfDay(2, 15, 0)));
3230
3231         assert(DateTime.fromISOExtString("0000-01-05T23:09:59") ==
3232                DateTime(Date(0, 1, 5), TimeOfDay(23, 9, 59)));
3233
3234         assert(DateTime.fromISOExtString("-0004-01-05T00:00:02") ==
3235                DateTime(Date(-4, 1, 5), TimeOfDay(0, 0, 2)));
3236
3237         assert(DateTime.fromISOExtString(" 2010-07-04T07:06:12 ") ==
3238                DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)));
3239     }
3240
3241     @safe unittest
3242     {
3243         assertThrown!DateTimeException(DateTime.fromISOExtString(""));
3244         assertThrown!DateTimeException(DateTime.fromISOExtString("20100704000000"));
3245         assertThrown!DateTimeException(DateTime.fromISOExtString("20100704 000000"));
3246         assertThrown!DateTimeException(DateTime.fromISOExtString("20100704t000000"));
3247         assertThrown!DateTimeException(DateTime.fromISOExtString("20100704T000000."));
3248         assertThrown!DateTimeException(DateTime.fromISOExtString("20100704T000000.0"));
3249
3250         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-07:0400:00:00"));
3251         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-07-04 00:00:00"));
3252         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-07-04 00:00:00"));
3253         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-07-04t00:00:00"));
3254         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-07-04T00:00:00."));
3255         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-07-04T00:00:00.0"));
3256
3257         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-Jul-0400:00:00"));
3258         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-Jul-04t00:00:00"));
3259         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-Jul-04 00:00:00."));
3260         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-Jul-04 00:00:00.0"));
3261
3262         assertThrown!DateTimeException(DateTime.fromISOExtString("20101222T172201"));
3263         assertThrown!DateTimeException(DateTime.fromISOExtString("2010-Dec-22 17:22:01"));
3264
3265         assert(DateTime.fromISOExtString("2010-12-22T17:22:01") == DateTime(Date(2010, 12, 22), TimeOfDay(17, 22, 01)));
3266         assert(DateTime.fromISOExtString("1999-07-06T12:30:33") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3267         assert(DateTime.fromISOExtString("-1999-07-06T12:30:33") == DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
3268         assert(DateTime.fromISOExtString("+01999-07-06T12:30:33") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3269         assert(DateTime.fromISOExtString("1999-07-06T12:30:33 ") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3270         assert(DateTime.fromISOExtString(" 1999-07-06T12:30:33") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3271         assert(DateTime.fromISOExtString(" 1999-07-06T12:30:33 ") == DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3272     }
3273
3274     // bug# 17801
3275     @safe unittest
3276     {
3277         import std.conv : to;
3278         import std.meta : AliasSeq;
3279         foreach (C; AliasSeq!(char, wchar, dchar))
3280         {
3281             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
3282                 assert(DateTime.fromISOExtString(to!S("2012-12-21T14:15:16")) == DateTime(2012, 12, 21, 14, 15, 16));
3283         }
3284     }
3285
3286
3287     /++
3288         Creates a $(LREF DateTime) from a string with the format
3289         YYYY-Mon-DD HH:MM:SS. Whitespace is stripped from the given string.
3290
3291         Params:
3292             simpleString = A string formatted in the way that toSimpleString
3293                            formats dates and times.
3294
3295         Throws:
3296             $(REF DateTimeException,std,datetime,date) if the given string is
3297             not in the correct format or if the resulting $(LREF DateTime)
3298             would not be valid.
3299       +/
3300     static DateTime fromSimpleString(S)(in S simpleString) @safe pure
3301         if (isSomeString!(S))
3302     {
3303         import std.algorithm.searching : countUntil;
3304         import std.exception : enforce;
3305         import std.format : format;
3306         import std.string : strip;
3307
3308         auto str = strip(simpleString);
3309
3310         enforce(str.length >= 15, new DateTimeException(format("Invalid string format: %s", simpleString)));
3311         auto t = str.countUntil(' ');
3312
3313         enforce(t != -1, new DateTimeException(format("Invalid string format: %s", simpleString)));
3314
3315         immutable date = Date.fromSimpleString(str[0 .. t]);
3316         immutable tod = TimeOfDay.fromISOExtString(str[t+1 .. $]);
3317
3318         return DateTime(date, tod);
3319     }
3320
3321     ///
3322     @safe unittest
3323     {
3324         assert(DateTime.fromSimpleString("2010-Jul-04 07:06:12") ==
3325                DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)));
3326         assert(DateTime.fromSimpleString("1998-Dec-25 02:15:00") ==
3327                DateTime(Date(1998, 12, 25), TimeOfDay(2, 15, 0)));
3328         assert(DateTime.fromSimpleString("0000-Jan-05 23:09:59") ==
3329                DateTime(Date(0, 1, 5), TimeOfDay(23, 9, 59)));
3330         assert(DateTime.fromSimpleString("-0004-Jan-05 00:00:02") ==
3331                DateTime(Date(-4, 1, 5), TimeOfDay(0, 0, 2)));
3332         assert(DateTime.fromSimpleString(" 2010-Jul-04 07:06:12 ") ==
3333                DateTime(Date(2010, 7, 4), TimeOfDay(7, 6, 12)));
3334     }
3335
3336     @safe unittest
3337     {
3338         assertThrown!DateTimeException(DateTime.fromISOString(""));
3339         assertThrown!DateTimeException(DateTime.fromISOString("20100704000000"));
3340         assertThrown!DateTimeException(DateTime.fromISOString("20100704 000000"));
3341         assertThrown!DateTimeException(DateTime.fromISOString("20100704t000000"));
3342         assertThrown!DateTimeException(DateTime.fromISOString("20100704T000000."));
3343         assertThrown!DateTimeException(DateTime.fromISOString("20100704T000000.0"));
3344
3345         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-0400:00:00"));
3346         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04 00:00:00"));
3347         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04t00:00:00"));
3348         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04T00:00:00."));
3349         assertThrown!DateTimeException(DateTime.fromISOString("2010-07-04T00:00:00.0"));
3350
3351         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-0400:00:00"));
3352         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04 00:00:00"));
3353         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04t00:00:00"));
3354         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04T00:00:00"));
3355         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04 00:00:00."));
3356         assertThrown!DateTimeException(DateTime.fromISOString("2010-Jul-04 00:00:00.0"));
3357
3358         assertThrown!DateTimeException(DateTime.fromSimpleString("20101222T172201"));
3359         assertThrown!DateTimeException(DateTime.fromSimpleString("2010-12-22T172201"));
3360
3361         assert(DateTime.fromSimpleString("2010-Dec-22 17:22:01") ==
3362                DateTime(Date(2010, 12, 22), TimeOfDay(17, 22, 01)));
3363         assert(DateTime.fromSimpleString("1999-Jul-06 12:30:33") ==
3364                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3365         assert(DateTime.fromSimpleString("-1999-Jul-06 12:30:33") ==
3366                DateTime(Date(-1999, 7, 6), TimeOfDay(12, 30, 33)));
3367         assert(DateTime.fromSimpleString("+01999-Jul-06 12:30:33") ==
3368                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3369         assert(DateTime.fromSimpleString("1999-Jul-06 12:30:33 ") ==
3370                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3371         assert(DateTime.fromSimpleString(" 1999-Jul-06 12:30:33") ==
3372                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3373         assert(DateTime.fromSimpleString(" 1999-Jul-06 12:30:33 ") ==
3374                DateTime(Date(1999, 7, 6), TimeOfDay(12, 30, 33)));
3375     }
3376
3377     // bug# 17801
3378     @safe unittest
3379     {
3380         import std.conv : to;
3381         import std.meta : AliasSeq;
3382         foreach (C; AliasSeq!(char, wchar, dchar))
3383         {
3384             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
3385                 assert(DateTime.fromSimpleString(to!S("2012-Dec-21 14:15:16")) == DateTime(2012, 12, 21, 14, 15, 16));
3386         }
3387     }
3388
3389
3390     /++
3391         Returns the $(LREF DateTime) farthest in the past which is representable
3392         by $(LREF DateTime).
3393       +/
3394     @property static DateTime min() @safe pure nothrow @nogc
3395     out(result)
3396     {
3397         assert(result._date == Date.min);
3398         assert(result._tod == TimeOfDay.min);
3399     }
3400     body
3401     {
3402         auto dt = DateTime.init;
3403         dt._date._year = short.min;
3404         dt._date._month = Month.jan;
3405         dt._date._day = 1;
3406
3407         return dt;
3408     }
3409
3410     @safe unittest
3411     {
3412         assert(DateTime.min.year < 0);
3413         assert(DateTime.min < DateTime.max);
3414     }
3415
3416
3417     /++
3418         Returns the $(LREF DateTime) farthest in the future which is
3419         representable by $(LREF DateTime).
3420       +/
3421     @property static DateTime max() @safe pure nothrow @nogc
3422     out(result)
3423     {
3424         assert(result._date == Date.max);
3425         assert(result._tod == TimeOfDay.max);
3426     }
3427     body
3428     {
3429         auto dt = DateTime.init;
3430         dt._date._year = short.max;
3431         dt._date._month = Month.dec;
3432         dt._date._day = 31;
3433         dt._tod._hour = TimeOfDay.maxHour;
3434         dt._tod._minute = TimeOfDay.maxMinute;
3435         dt._tod._second = TimeOfDay.maxSecond;
3436
3437         return dt;
3438     }
3439
3440     @safe unittest
3441     {
3442         assert(DateTime.max.year > 0);
3443         assert(DateTime.max > DateTime.min);
3444     }
3445
3446
3447 private:
3448
3449     /+
3450         Add seconds to the time of day. Negative values will subtract. If the
3451         number of seconds overflows (or underflows), then the seconds will wrap,
3452         increasing (or decreasing) the number of minutes accordingly. The
3453         same goes for any larger units.
3454
3455         Params:
3456             seconds = The number of seconds to add to this $(LREF DateTime).
3457       +/
3458     ref DateTime _addSeconds(long seconds) return @safe pure nothrow @nogc
3459     {
3460         long hnsecs = convert!("seconds", "hnsecs")(seconds);
3461         hnsecs += convert!("hours", "hnsecs")(_tod._hour);
3462         hnsecs += convert!("minutes", "hnsecs")(_tod._minute);
3463         hnsecs += convert!("seconds", "hnsecs")(_tod._second);
3464
3465         auto days = splitUnitsFromHNSecs!"days"(hnsecs);
3466
3467         if (hnsecs < 0)
3468         {
3469             hnsecs += convert!("days", "hnsecs")(1);
3470             --days;
3471         }
3472
3473         _date._addDays(days);
3474
3475         immutable newHours = splitUnitsFromHNSecs!"hours"(hnsecs);
3476         immutable newMinutes = splitUnitsFromHNSecs!"minutes"(hnsecs);
3477         immutable newSeconds = splitUnitsFromHNSecs!"seconds"(hnsecs);
3478
3479         _tod._hour = cast(ubyte) newHours;
3480         _tod._minute = cast(ubyte) newMinutes;
3481         _tod._second = cast(ubyte) newSeconds;
3482
3483         return this;
3484     }
3485
3486     @safe unittest
3487     {
3488         static void testDT(DateTime orig, int seconds, in DateTime expected, size_t line = __LINE__)
3489         {
3490             orig._addSeconds(seconds);
3491             assert(orig == expected);
3492         }
3493
3494         // Test A.D.
3495         testDT(DateTime(1999, 7, 6, 12, 30, 33), 0, DateTime(1999, 7, 6, 12, 30, 33));
3496         testDT(DateTime(1999, 7, 6, 12, 30, 33), 1, DateTime(1999, 7, 6, 12, 30, 34));
3497         testDT(DateTime(1999, 7, 6, 12, 30, 33), 2, DateTime(1999, 7, 6, 12, 30, 35));
3498         testDT(DateTime(1999, 7, 6, 12, 30, 33), 3, DateTime(1999, 7, 6, 12, 30, 36));
3499         testDT(DateTime(1999, 7, 6, 12, 30, 33), 4, DateTime(1999, 7, 6, 12, 30, 37));
3500         testDT(DateTime(1999, 7, 6, 12, 30, 33), 5, DateTime(1999, 7, 6, 12, 30, 38));
3501         testDT(DateTime(1999, 7, 6, 12, 30, 33), 10, DateTime(1999, 7, 6, 12, 30, 43));
3502         testDT(DateTime(1999, 7, 6, 12, 30, 33), 15, DateTime(1999, 7, 6, 12, 30, 48));
3503         testDT(DateTime(1999, 7, 6, 12, 30, 33), 26, DateTime(1999, 7, 6, 12, 30, 59));
3504         testDT(DateTime(1999, 7, 6, 12, 30, 33), 27, DateTime(1999, 7, 6, 12, 31, 0));
3505         testDT(DateTime(1999, 7, 6, 12, 30, 33), 30, DateTime(1999, 7, 6, 12, 31, 3));
3506         testDT(DateTime(1999, 7, 6, 12, 30, 33), 59, DateTime(1999, 7, 6, 12, 31, 32));
3507         testDT(DateTime(1999, 7, 6, 12, 30, 33), 60, DateTime(1999, 7, 6, 12, 31, 33));
3508         testDT(DateTime(1999, 7, 6, 12, 30, 33), 61, DateTime(1999, 7, 6, 12, 31, 34));
3509
3510         testDT(DateTime(1999, 7, 6, 12, 30, 33), 1766, DateTime(1999, 7, 6, 12, 59, 59));
3511         testDT(DateTime(1999, 7, 6, 12, 30, 33), 1767, DateTime(1999, 7, 6, 13, 0, 0));
3512         testDT(DateTime(1999, 7, 6, 12, 30, 33), 1768, DateTime(1999, 7, 6, 13, 0, 1));
3513         testDT(DateTime(1999, 7, 6, 12, 30, 33), 2007, DateTime(1999, 7, 6, 13, 4, 0));
3514         testDT(DateTime(1999, 7, 6, 12, 30, 33), 3599, DateTime(1999, 7, 6, 13, 30, 32));
3515         testDT(DateTime(1999, 7, 6, 12, 30, 33), 3600, DateTime(1999, 7, 6, 13, 30, 33));
3516         testDT(DateTime(1999, 7, 6, 12, 30, 33), 3601, DateTime(1999, 7, 6, 13, 30, 34));
3517         testDT(DateTime(1999, 7, 6, 12, 30, 33), 7200, DateTime(1999, 7, 6, 14, 30, 33));
3518         testDT(DateTime(1999, 7, 6, 23, 0, 0), 432_123, DateTime(1999, 7, 11, 23, 2, 3));
3519
3520         testDT(DateTime(1999, 7, 6, 12, 30, 33), -1, DateTime(1999, 7, 6, 12, 30, 32));
3521         testDT(DateTime(1999, 7, 6, 12, 30, 33), -2, DateTime(1999, 7, 6, 12, 30, 31));
3522         testDT(DateTime(1999, 7, 6, 12, 30, 33), -3, DateTime(1999, 7, 6, 12, 30, 30));
3523         testDT(DateTime(1999, 7, 6, 12, 30, 33), -4, DateTime(1999, 7, 6, 12, 30, 29));
3524         testDT(DateTime(1999, 7, 6, 12, 30, 33), -5, DateTime(1999, 7, 6, 12, 30, 28));
3525         testDT(DateTime(1999, 7, 6, 12, 30, 33), -10, DateTime(1999, 7, 6, 12, 30, 23));
3526         testDT(DateTime(1999, 7, 6, 12, 30, 33), -15, DateTime(1999, 7, 6, 12, 30, 18));
3527         testDT(DateTime(1999, 7, 6, 12, 30, 33), -33, DateTime(1999, 7, 6, 12, 30, 0));
3528         testDT(DateTime(1999, 7, 6, 12, 30, 33), -34, DateTime(1999, 7, 6, 12, 29, 59));
3529         testDT(DateTime(1999, 7, 6, 12, 30, 33), -35, DateTime(1999, 7, 6, 12, 29, 58));
3530         testDT(DateTime(1999, 7, 6, 12, 30, 33), -59, DateTime(1999, 7, 6, 12, 29, 34));
3531         testDT(DateTime(1999, 7, 6, 12, 30, 33), -60, DateTime(1999, 7, 6, 12, 29, 33));
3532         testDT(DateTime(1999, 7, 6, 12, 30, 33), -61, DateTime(1999, 7, 6, 12, 29, 32));
3533
3534         testDT(DateTime(1999, 7, 6, 12, 30, 33), -1833, DateTime(1999, 7, 6, 12, 0, 0));
3535         testDT(DateTime(1999, 7, 6, 12, 30, 33), -1834, DateTime(1999, 7, 6, 11, 59, 59));
3536         testDT(DateTime(1999, 7, 6, 12, 30, 33), -3600, DateTime(1999, 7, 6, 11, 30, 33));
3537         testDT(DateTime(1999, 7, 6, 12, 30, 33), -3601, DateTime(1999, 7, 6, 11, 30, 32));
3538         testDT(DateTime(1999, 7, 6, 12, 30, 33), -5134, DateTime(1999, 7, 6, 11, 4, 59));
3539         testDT(DateTime(1999, 7, 6, 23, 0, 0), -432_123, DateTime(1999, 7, 1, 22, 57, 57));
3540
3541         testDT(DateTime(1999, 7, 6, 12, 30, 0), 1, DateTime(1999, 7, 6, 12, 30, 1));
3542         testDT(DateTime(1999, 7, 6, 12, 30, 0), 0, DateTime(1999, 7, 6, 12, 30, 0));
3543         testDT(DateTime(1999, 7, 6, 12, 30, 0), -1, DateTime(1999, 7, 6, 12, 29, 59));
3544
3545         testDT(DateTime(1999, 7, 6, 12, 0, 0), 1, DateTime(1999, 7, 6, 12, 0, 1));
3546         testDT(DateTime(1999, 7, 6, 12, 0, 0), 0, DateTime(1999, 7, 6, 12, 0, 0));
3547         testDT(DateTime(1999, 7, 6, 12, 0, 0), -1, DateTime(1999, 7, 6, 11, 59, 59));
3548
3549         testDT(DateTime(1999, 7, 6, 0, 0, 0), 1, DateTime(1999, 7, 6, 0, 0, 1));
3550         testDT(DateTime(1999, 7, 6, 0, 0, 0), 0, DateTime(1999, 7, 6, 0, 0, 0));
3551         testDT(DateTime(1999, 7, 6, 0, 0, 0), -1, DateTime(1999, 7, 5, 23, 59, 59));
3552
3553         testDT(DateTime(1999, 7, 5, 23, 59, 59), 1, DateTime(1999, 7, 6, 0, 0, 0));
3554         testDT(DateTime(1999, 7, 5, 23, 59, 59), 0, DateTime(1999, 7, 5, 23, 59, 59));
3555         testDT(DateTime(1999, 7, 5, 23, 59, 59), -1, DateTime(1999, 7, 5, 23, 59, 58));
3556
3557         testDT(DateTime(1998, 12, 31, 23, 59, 59), 1, DateTime(1999, 1, 1, 0, 0, 0));
3558         testDT(DateTime(1998, 12, 31, 23, 59, 59), 0, DateTime(1998, 12, 31, 23, 59, 59));
3559         testDT(DateTime(1998, 12, 31, 23, 59, 59), -1, DateTime(1998, 12, 31, 23, 59, 58));
3560
3561         testDT(DateTime(1998, 1, 1, 0, 0, 0), 1, DateTime(1998, 1, 1, 0, 0, 1));
3562         testDT(DateTime(1998, 1, 1, 0, 0, 0), 0, DateTime(1998, 1, 1, 0, 0, 0));
3563         testDT(DateTime(1998, 1, 1, 0, 0, 0), -1, DateTime(1997, 12, 31, 23, 59, 59));
3564
3565         // Test B.C.
3566         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 0, DateTime(-1999, 7, 6, 12, 30, 33));
3567         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 1, DateTime(-1999, 7, 6, 12, 30, 34));
3568         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 2, DateTime(-1999, 7, 6, 12, 30, 35));
3569         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 3, DateTime(-1999, 7, 6, 12, 30, 36));
3570         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 4, DateTime(-1999, 7, 6, 12, 30, 37));
3571         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 5, DateTime(-1999, 7, 6, 12, 30, 38));
3572         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 10, DateTime(-1999, 7, 6, 12, 30, 43));
3573         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 15, DateTime(-1999, 7, 6, 12, 30, 48));
3574         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 26, DateTime(-1999, 7, 6, 12, 30, 59));
3575         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 27, DateTime(-1999, 7, 6, 12, 31, 0));
3576         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 30, DateTime(-1999, 7, 6, 12, 31, 3));
3577         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 59, DateTime(-1999, 7, 6, 12, 31, 32));
3578         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 60, DateTime(-1999, 7, 6, 12, 31, 33));
3579         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 61, DateTime(-1999, 7, 6, 12, 31, 34));
3580
3581         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 1766, DateTime(-1999, 7, 6, 12, 59, 59));
3582         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 1767, DateTime(-1999, 7, 6, 13, 0, 0));
3583         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 1768, DateTime(-1999, 7, 6, 13, 0, 1));
3584         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 2007, DateTime(-1999, 7, 6, 13, 4, 0));
3585         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 3599, DateTime(-1999, 7, 6, 13, 30, 32));
3586         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 3600, DateTime(-1999, 7, 6, 13, 30, 33));
3587         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 3601, DateTime(-1999, 7, 6, 13, 30, 34));
3588         testDT(DateTime(-1999, 7, 6, 12, 30, 33), 7200, DateTime(-1999, 7, 6, 14, 30, 33));
3589         testDT(DateTime(-1999, 7, 6, 23, 0, 0), 432_123, DateTime(-1999, 7, 11, 23, 2, 3));
3590
3591         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -1, DateTime(-1999, 7, 6, 12, 30, 32));
3592         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -2, DateTime(-1999, 7, 6, 12, 30, 31));
3593         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -3, DateTime(-1999, 7, 6, 12, 30, 30));
3594         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -4, DateTime(-1999, 7, 6, 12, 30, 29));
3595         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -5, DateTime(-1999, 7, 6, 12, 30, 28));
3596         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -10, DateTime(-1999, 7, 6, 12, 30, 23));
3597         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -15, DateTime(-1999, 7, 6, 12, 30, 18));
3598         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -33, DateTime(-1999, 7, 6, 12, 30, 0));
3599         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -34, DateTime(-1999, 7, 6, 12, 29, 59));
3600         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -35, DateTime(-1999, 7, 6, 12, 29, 58));
3601         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -59, DateTime(-1999, 7, 6, 12, 29, 34));
3602         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -60, DateTime(-1999, 7, 6, 12, 29, 33));
3603         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -61, DateTime(-1999, 7, 6, 12, 29, 32));
3604
3605         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -1833, DateTime(-1999, 7, 6, 12, 0, 0));
3606         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -1834, DateTime(-1999, 7, 6, 11, 59, 59));
3607         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -3600, DateTime(-1999, 7, 6, 11, 30, 33));
3608         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -3601, DateTime(-1999, 7, 6, 11, 30, 32));
3609         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -5134, DateTime(-1999, 7, 6, 11, 4, 59));
3610         testDT(DateTime(-1999, 7, 6, 12, 30, 33), -7200, DateTime(-1999, 7, 6, 10, 30, 33));
3611         testDT(DateTime(-1999, 7, 6, 23, 0, 0), -432_123, DateTime(-1999, 7, 1, 22, 57, 57));
3612
3613         testDT(DateTime(-1999, 7, 6, 12, 30, 0), 1, DateTime(-1999, 7, 6, 12, 30, 1));
3614         testDT(DateTime(-1999, 7, 6, 12, 30, 0), 0, DateTime(-1999, 7, 6, 12, 30, 0));
3615         testDT(DateTime(-1999, 7, 6, 12, 30, 0), -1, DateTime(-1999, 7, 6, 12, 29, 59));
3616
3617         testDT(DateTime(-1999, 7, 6, 12, 0, 0), 1, DateTime(-1999, 7, 6, 12, 0, 1));
3618         testDT(DateTime(-1999, 7, 6, 12, 0, 0), 0, DateTime(-1999, 7, 6, 12, 0, 0));
3619         testDT(DateTime(-1999, 7, 6, 12, 0, 0), -1, DateTime(-1999, 7, 6, 11, 59, 59));
3620
3621         testDT(DateTime(-1999, 7, 6, 0, 0, 0), 1, DateTime(-1999, 7, 6, 0, 0, 1));
3622         testDT(DateTime(-1999, 7, 6, 0, 0, 0), 0, DateTime(-1999, 7, 6, 0, 0, 0));
3623         testDT(DateTime(-1999, 7, 6, 0, 0, 0), -1, DateTime(-1999, 7, 5, 23, 59, 59));
3624
3625         testDT(DateTime(-1999, 7, 5, 23, 59, 59), 1, DateTime(-1999, 7, 6, 0, 0, 0));
3626         testDT(DateTime(-1999, 7, 5, 23, 59, 59), 0, DateTime(-1999, 7, 5, 23, 59, 59));
3627         testDT(DateTime(-1999, 7, 5, 23, 59, 59), -1, DateTime(-1999, 7, 5, 23, 59, 58));
3628
3629         testDT(DateTime(-2000, 12, 31, 23, 59, 59), 1, DateTime(-1999, 1, 1, 0, 0, 0));
3630         testDT(DateTime(-2000, 12, 31, 23, 59, 59), 0, DateTime(-2000, 12, 31, 23, 59, 59));
3631         testDT(DateTime(-2000, 12, 31, 23, 59, 59), -1, DateTime(-2000, 12, 31, 23, 59, 58));
3632
3633         testDT(DateTime(-2000, 1, 1, 0, 0, 0), 1, DateTime(-2000, 1, 1, 0, 0, 1));
3634         testDT(DateTime(-2000, 1, 1, 0, 0, 0), 0, DateTime(-2000, 1, 1, 0, 0, 0));
3635         testDT(DateTime(-2000, 1, 1, 0, 0, 0), -1, DateTime(-2001, 12, 31, 23, 59, 59));
3636
3637         // Test Both
3638         testDT(DateTime(1, 1, 1, 0, 0, 0), -1, DateTime(0, 12, 31, 23, 59, 59));
3639         testDT(DateTime(0, 12, 31, 23, 59, 59), 1, DateTime(1, 1, 1, 0, 0, 0));
3640
3641         testDT(DateTime(0, 1, 1, 0, 0, 0), -1, DateTime(-1, 12, 31, 23, 59, 59));
3642         testDT(DateTime(-1, 12, 31, 23, 59, 59), 1, DateTime(0, 1, 1, 0, 0, 0));
3643
3644         testDT(DateTime(-1, 1, 1, 11, 30, 33), 63_165_600L, DateTime(1, 1, 1, 13, 30, 33));
3645         testDT(DateTime(1, 1, 1, 13, 30, 33), -63_165_600L, DateTime(-1, 1, 1, 11, 30, 33));
3646
3647         testDT(DateTime(-1, 1, 1, 11, 30, 33), 63_165_617L, DateTime(1, 1, 1, 13, 30, 50));
3648         testDT(DateTime(1, 1, 1, 13, 30, 50), -63_165_617L, DateTime(-1, 1, 1, 11, 30, 33));
3649
3650         const cdt = DateTime(1999, 7, 6, 12, 30, 33);
3651         immutable idt = DateTime(1999, 7, 6, 12, 30, 33);
3652         static assert(!__traits(compiles, cdt._addSeconds(4)));
3653         static assert(!__traits(compiles, idt._addSeconds(4)));
3654     }
3655
3656
3657     Date      _date;
3658     TimeOfDay _tod;
3659 }
3660
3661
3662 /++
3663     Represents a date in the
3664     $(HTTP en.wikipedia.org/wiki/Proleptic_Gregorian_calendar, Proleptic
3665     Gregorian Calendar) ranging from 32,768 B.C. to 32,767 A.D. Positive years
3666     are A.D. Non-positive years are B.C.
3667
3668     Year, month, and day are kept separately internally so that $(D Date) is
3669     optimized for calendar-based operations.
3670
3671     $(D Date) uses the Proleptic Gregorian Calendar, so it assumes the Gregorian
3672     leap year calculations for its entire length. As per
3673     $(HTTP en.wikipedia.org/wiki/ISO_8601, ISO 8601), it treats 1 B.C. as
3674     year 0, i.e. 1 B.C. is 0, 2 B.C. is -1, etc. Use $(LREF yearBC) to use B.C.
3675     as a positive integer with 1 B.C. being the year prior to 1 A.D.
3676
3677     Year 0 is a leap year.
3678  +/
3679 struct Date
3680 {
3681 public:
3682
3683     /++
3684         Throws:
3685             $(REF DateTimeException,std,datetime,date) if the resulting
3686             $(LREF Date) would not be valid.
3687
3688         Params:
3689             year  = Year of the Gregorian Calendar. Positive values are A.D.
3690                     Non-positive values are B.C. with year 0 being the year
3691                     prior to 1 A.D.
3692             month = Month of the year (January is 1).
3693             day   = Day of the month.
3694      +/
3695     this(int year, int month, int day) @safe pure
3696     {
3697         enforceValid!"months"(cast(Month) month);
3698         enforceValid!"days"(year, cast(Month) month, day);
3699
3700         _year  = cast(short) year;
3701         _month = cast(Month) month;
3702         _day   = cast(ubyte) day;
3703     }
3704
3705     @safe unittest
3706     {
3707         import std.exception : assertNotThrown;
3708         assert(Date(1, 1, 1) == Date.init);
3709
3710         static void testDate(in Date date, int year, int month, int day)
3711         {
3712             assert(date._year == year);
3713             assert(date._month == month);
3714             assert(date._day == day);
3715         }
3716
3717         testDate(Date(1999, 1 , 1), 1999, Month.jan, 1);
3718         testDate(Date(1999, 7 , 1), 1999, Month.jul, 1);
3719         testDate(Date(1999, 7 , 6), 1999, Month.jul, 6);
3720
3721         // Test A.D.
3722         assertThrown!DateTimeException(Date(1, 0, 1));
3723         assertThrown!DateTimeException(Date(1, 1, 0));
3724         assertThrown!DateTimeException(Date(1999, 13, 1));
3725         assertThrown!DateTimeException(Date(1999, 1, 32));
3726         assertThrown!DateTimeException(Date(1999, 2, 29));
3727         assertThrown!DateTimeException(Date(2000, 2, 30));
3728         assertThrown!DateTimeException(Date(1999, 3, 32));
3729         assertThrown!DateTimeException(Date(1999, 4, 31));
3730         assertThrown!DateTimeException(Date(1999, 5, 32));
3731         assertThrown!DateTimeException(Date(1999, 6, 31));
3732         assertThrown!DateTimeException(Date(1999, 7, 32));
3733         assertThrown!DateTimeException(Date(1999, 8, 32));
3734         assertThrown!DateTimeException(Date(1999, 9, 31));
3735         assertThrown!DateTimeException(Date(1999, 10, 32));
3736         assertThrown!DateTimeException(Date(1999, 11, 31));
3737         assertThrown!DateTimeException(Date(1999, 12, 32));
3738
3739         assertNotThrown!DateTimeException(Date(1999, 1, 31));
3740         assertNotThrown!DateTimeException(Date(1999, 2, 28));
3741         assertNotThrown!DateTimeException(Date(2000, 2, 29));
3742         assertNotThrown!DateTimeException(Date(1999, 3, 31));
3743         assertNotThrown!DateTimeException(Date(1999, 4, 30));
3744         assertNotThrown!DateTimeException(Date(1999, 5, 31));
3745         assertNotThrown!DateTimeException(Date(1999, 6, 30));
3746         assertNotThrown!DateTimeException(Date(1999, 7, 31));
3747         assertNotThrown!DateTimeException(Date(1999, 8, 31));
3748         assertNotThrown!DateTimeException(Date(1999, 9, 30));
3749         assertNotThrown!DateTimeException(Date(1999, 10, 31));
3750         assertNotThrown!DateTimeException(Date(1999, 11, 30));
3751         assertNotThrown!DateTimeException(Date(1999, 12, 31));
3752
3753         // Test B.C.
3754         assertNotThrown!DateTimeException(Date(0, 1, 1));
3755         assertNotThrown!DateTimeException(Date(-1, 1, 1));
3756         assertNotThrown!DateTimeException(Date(-1, 12, 31));
3757         assertNotThrown!DateTimeException(Date(-1, 2, 28));
3758         assertNotThrown!DateTimeException(Date(-4, 2, 29));
3759
3760         assertThrown!DateTimeException(Date(-1, 2, 29));
3761         assertThrown!DateTimeException(Date(-2, 2, 29));
3762         assertThrown!DateTimeException(Date(-3, 2, 29));
3763     }
3764
3765
3766     /++
3767         Params:
3768             day = The Xth day of the Gregorian Calendar that the constructed
3769                   $(LREF Date) will be for.
3770      +/
3771     this(int day) @safe pure nothrow @nogc
3772     {
3773         if (day > 0)
3774         {
3775             int years = (day / daysIn400Years) * 400 + 1;
3776             day %= daysIn400Years;
3777
3778             {
3779                 immutable tempYears = day / daysIn100Years;
3780
3781                 if (tempYears == 4)
3782                 {
3783                     years += 300;
3784                     day -= daysIn100Years * 3;
3785                 }
3786                 else
3787                 {
3788                     years += tempYears * 100;
3789                     day %= daysIn100Years;
3790                 }
3791             }
3792
3793             years += (day / daysIn4Years) * 4;
3794             day %= daysIn4Years;
3795
3796             {
3797                 immutable tempYears = day / daysInYear;
3798
3799                 if (tempYears == 4)
3800                 {
3801                     years += 3;
3802                     day -= daysInYear * 3;
3803                 }
3804                 else
3805                 {
3806                     years += tempYears;
3807                     day %= daysInYear;
3808                 }
3809             }
3810
3811             if (day == 0)
3812             {
3813                 _year = cast(short)(years - 1);
3814                 _month = Month.dec;
3815                 _day = 31;
3816             }
3817             else
3818             {
3819                 _year = cast(short) years;
3820
3821                 setDayOfYear(day);
3822             }
3823         }
3824         else if (day <= 0 && -day < daysInLeapYear)
3825         {
3826             _year = 0;
3827
3828             setDayOfYear(daysInLeapYear + day);
3829         }
3830         else
3831         {
3832             day += daysInLeapYear - 1;
3833             int years = (day / daysIn400Years) * 400 - 1;
3834             day %= daysIn400Years;
3835
3836             {
3837                 immutable tempYears = day / daysIn100Years;
3838
3839                 if (tempYears == -4)
3840                 {
3841                     years -= 300;
3842                     day += daysIn100Years * 3;
3843                 }
3844                 else
3845                 {
3846                     years += tempYears * 100;
3847                     day %= daysIn100Years;
3848                 }
3849             }
3850
3851             years += (day / daysIn4Years) * 4;
3852             day %= daysIn4Years;
3853
3854             {
3855                 immutable tempYears = day / daysInYear;
3856
3857                 if (tempYears == -4)
3858                 {
3859                     years -= 3;
3860                     day += daysInYear * 3;
3861                 }
3862                 else
3863                 {
3864                     years += tempYears;
3865                     day %= daysInYear;
3866                 }
3867             }
3868
3869             if (day == 0)
3870             {
3871                 _year = cast(short)(years + 1);
3872                 _month = Month.jan;
3873                 _day = 1;
3874             }
3875             else
3876             {
3877                 _year = cast(short) years;
3878                 immutable newDoY = (yearIsLeapYear(_year) ? daysInLeapYear : daysInYear) + day + 1;
3879
3880                 setDayOfYear(newDoY);
3881             }
3882         }
3883     }
3884
3885     @safe unittest
3886     {
3887         import std.range : chain;
3888
3889         // Test A.D.
3890         foreach (gd; chain(testGregDaysBC, testGregDaysAD))
3891             assert(Date(gd.day) == gd.date);
3892     }
3893
3894
3895     /++
3896         Compares this $(LREF Date) with the given $(LREF Date).
3897
3898         Returns:
3899             $(BOOKTABLE,
3900             $(TR $(TD this &lt; rhs) $(TD &lt; 0))
3901             $(TR $(TD this == rhs) $(TD 0))
3902             $(TR $(TD this &gt; rhs) $(TD &gt; 0))
3903             )
3904      +/
3905     int opCmp(in Date rhs) const @safe pure nothrow @nogc
3906     {
3907         if (_year < rhs._year)
3908             return -1;
3909         if (_year > rhs._year)
3910             return 1;
3911
3912         if (_month < rhs._month)
3913             return -1;
3914         if (_month > rhs._month)
3915             return 1;
3916
3917         if (_day < rhs._day)
3918             return -1;
3919         if (_day > rhs._day)
3920             return 1;
3921
3922         return 0;
3923     }
3924
3925     @safe unittest
3926     {
3927         // Test A.D.
3928         assert(Date(1, 1, 1).opCmp(Date.init) == 0);
3929
3930         assert(Date(1999, 1, 1).opCmp(Date(1999, 1, 1)) == 0);
3931         assert(Date(1, 7, 1).opCmp(Date(1, 7, 1)) == 0);
3932         assert(Date(1, 1, 6).opCmp(Date(1, 1, 6)) == 0);
3933
3934         assert(Date(1999, 7, 1).opCmp(Date(1999, 7, 1)) == 0);
3935         assert(Date(1999, 7, 6).opCmp(Date(1999, 7, 6)) == 0);
3936
3937         assert(Date(1, 7, 6).opCmp(Date(1, 7, 6)) == 0);
3938
3939         assert(Date(1999, 7, 6).opCmp(Date(2000, 7, 6)) < 0);
3940         assert(Date(2000, 7, 6).opCmp(Date(1999, 7, 6)) > 0);
3941         assert(Date(1999, 7, 6).opCmp(Date(1999, 8, 6)) < 0);
3942         assert(Date(1999, 8, 6).opCmp(Date(1999, 7, 6)) > 0);
3943         assert(Date(1999, 7, 6).opCmp(Date(1999, 7, 7)) < 0);
3944         assert(Date(1999, 7, 7).opCmp(Date(1999, 7, 6)) > 0);
3945
3946         assert(Date(1999, 8, 7).opCmp(Date(2000, 7, 6)) < 0);
3947         assert(Date(2000, 8, 6).opCmp(Date(1999, 7, 7)) > 0);
3948         assert(Date(1999, 7, 7).opCmp(Date(2000, 7, 6)) < 0);
3949         assert(Date(2000, 7, 6).opCmp(Date(1999, 7, 7)) > 0);
3950         assert(Date(1999, 7, 7).opCmp(Date(1999, 8, 6)) < 0);
3951         assert(Date(1999, 8, 6).opCmp(Date(1999, 7, 7)) > 0);
3952
3953         // Test B.C.
3954         assert(Date(0, 1, 1).opCmp(Date(0, 1, 1)) == 0);
3955         assert(Date(-1, 1, 1).opCmp(Date(-1, 1, 1)) == 0);
3956         assert(Date(-1, 7, 1).opCmp(Date(-1, 7, 1)) == 0);
3957         assert(Date(-1, 1, 6).opCmp(Date(-1, 1, 6)) == 0);
3958
3959         assert(Date(-1999, 7, 1).opCmp(Date(-1999, 7, 1)) == 0);
3960         assert(Date(-1999, 7, 6).opCmp(Date(-1999, 7, 6)) == 0);
3961
3962         assert(Date(-1, 7, 6).opCmp(Date(-1, 7, 6)) == 0);
3963
3964         assert(Date(-2000, 7, 6).opCmp(Date(-1999, 7, 6)) < 0);
3965         assert(Date(-1999, 7, 6).opCmp(Date(-2000, 7, 6)) > 0);
3966         assert(Date(-1999, 7, 6).opCmp(Date(-1999, 8, 6)) < 0);
3967         assert(Date(-1999, 8, 6).opCmp(Date(-1999, 7, 6)) > 0);
3968         assert(Date(-1999, 7, 6).opCmp(Date(-1999, 7, 7)) < 0);
3969         assert(Date(-1999, 7, 7).opCmp(Date(-1999, 7, 6)) > 0);
3970
3971         assert(Date(-2000, 8, 6).opCmp(Date(-1999, 7, 7)) < 0);
3972         assert(Date(-1999, 8, 7).opCmp(Date(-2000, 7, 6)) > 0);
3973         assert(Date(-2000, 7, 6).opCmp(Date(-1999, 7, 7)) < 0);
3974         assert(Date(-1999, 7, 7).opCmp(Date(-2000, 7, 6)) > 0);
3975         assert(Date(-1999, 7, 7).opCmp(Date(-1999, 8, 6)) < 0);
3976         assert(Date(-1999, 8, 6).opCmp(Date(-1999, 7, 7)) > 0);
3977
3978         // Test Both
3979         assert(Date(-1999, 7, 6).opCmp(Date(1999, 7, 6)) < 0);
3980         assert(Date(1999, 7, 6).opCmp(Date(-1999, 7, 6)) > 0);
3981
3982         assert(Date(-1999, 8, 6).opCmp(Date(1999, 7, 6)) < 0);
3983         assert(Date(1999, 7, 6).opCmp(Date(-1999, 8, 6)) > 0);
3984
3985         assert(Date(-1999, 7, 7).opCmp(Date(1999, 7, 6)) < 0);
3986         assert(Date(1999, 7, 6).opCmp(Date(-1999, 7, 7)) > 0);
3987
3988         assert(Date(-1999, 8, 7).opCmp(Date(1999, 7, 6)) < 0);
3989         assert(Date(1999, 7, 6).opCmp(Date(-1999, 8, 7)) > 0);
3990
3991         assert(Date(-1999, 8, 6).opCmp(Date(1999, 6, 6)) < 0);
3992         assert(Date(1999, 6, 8).opCmp(Date(-1999, 7, 6)) > 0);
3993
3994         auto date = Date(1999, 7, 6);
3995         const cdate = Date(1999, 7, 6);
3996         immutable idate = Date(1999, 7, 6);
3997         assert(date.opCmp(date) == 0);
3998         assert(date.opCmp(cdate) == 0);
3999         assert(date.opCmp(idate) == 0);
4000         assert(cdate.opCmp(date) == 0);
4001         assert(cdate.opCmp(cdate) == 0);
4002         assert(cdate.opCmp(idate) == 0);
4003         assert(idate.opCmp(date) == 0);
4004         assert(idate.opCmp(cdate) == 0);
4005         assert(idate.opCmp(idate) == 0);
4006     }
4007
4008
4009     /++
4010         Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
4011         are B.C.
4012      +/
4013     @property short year() const @safe pure nothrow @nogc
4014     {
4015         return _year;
4016     }
4017
4018     ///
4019     @safe unittest
4020     {
4021         assert(Date(1999, 7, 6).year == 1999);
4022         assert(Date(2010, 10, 4).year == 2010);
4023         assert(Date(-7, 4, 5).year == -7);
4024     }
4025
4026     @safe unittest
4027     {
4028         assert(Date.init.year == 1);
4029         assert(Date(1999, 7, 6).year == 1999);
4030         assert(Date(-1999, 7, 6).year == -1999);
4031
4032         const cdate = Date(1999, 7, 6);
4033         immutable idate = Date(1999, 7, 6);
4034         assert(cdate.year == 1999);
4035         assert(idate.year == 1999);
4036     }
4037
4038     /++
4039         Year of the Gregorian Calendar. Positive numbers are A.D. Non-positive
4040         are B.C.
4041
4042         Params:
4043             year = The year to set this Date's year to.
4044
4045         Throws:
4046             $(REF DateTimeException,std,datetime,date) if the new year is not
4047             a leap year and the resulting date would be on February 29th.
4048      +/
4049     @property void year(int year) @safe pure
4050     {
4051         enforceValid!"days"(year, _month, _day);
4052         _year = cast(short) year;
4053     }
4054
4055     ///
4056     @safe unittest
4057     {
4058         assert(Date(1999, 7, 6).year == 1999);
4059         assert(Date(2010, 10, 4).year == 2010);
4060         assert(Date(-7, 4, 5).year == -7);
4061     }
4062
4063     @safe unittest
4064     {
4065         static void testDateInvalid(Date date, int year)
4066         {
4067             date.year = year;
4068         }
4069
4070         static void testDate(Date date, int year, in Date expected)
4071         {
4072             date.year = year;
4073             assert(date == expected);
4074         }
4075
4076         assertThrown!DateTimeException(testDateInvalid(Date(4, 2, 29), 1));
4077
4078         testDate(Date(1, 1, 1), 1999, Date(1999, 1, 1));
4079         testDate(Date(1, 1, 1), 0, Date(0, 1, 1));
4080         testDate(Date(1, 1, 1), -1999, Date(-1999, 1, 1));
4081
4082         const cdate = Date(1999, 7, 6);
4083         immutable idate = Date(1999, 7, 6);
4084         static assert(!__traits(compiles, cdate.year = 1999));
4085         static assert(!__traits(compiles, idate.year = 1999));
4086     }
4087
4088
4089     /++
4090         Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
4091
4092         Throws:
4093             $(REF DateTimeException,std,datetime,date) if $(D isAD) is true.
4094      +/
4095     @property ushort yearBC() const @safe pure
4096     {
4097         import std.format : format;
4098
4099         if (isAD)
4100             throw new DateTimeException(format("Year %s is A.D.", _year));
4101         return cast(ushort)((_year * -1) + 1);
4102     }
4103
4104     ///
4105     @safe unittest
4106     {
4107         assert(Date(0, 1, 1).yearBC == 1);
4108         assert(Date(-1, 1, 1).yearBC == 2);
4109         assert(Date(-100, 1, 1).yearBC == 101);
4110     }
4111
4112     @safe unittest
4113     {
4114         assertThrown!DateTimeException((in Date date){date.yearBC;}(Date(1, 1, 1)));
4115
4116         auto date = Date(0, 7, 6);
4117         const cdate = Date(0, 7, 6);
4118         immutable idate = Date(0, 7, 6);
4119         assert(date.yearBC == 1);
4120         assert(cdate.yearBC == 1);
4121         assert(idate.yearBC == 1);
4122     }
4123
4124
4125     /++
4126         Year B.C. of the Gregorian Calendar counting year 0 as 1 B.C.
4127
4128         Params:
4129             year = The year B.C. to set this $(LREF Date)'s year to.
4130
4131         Throws:
4132             $(REF DateTimeException,std,datetime,date) if a non-positive value
4133             is given.
4134      +/
4135     @property void yearBC(int year) @safe pure
4136     {
4137         if (year <= 0)
4138             throw new DateTimeException("The given year is not a year B.C.");
4139         _year = cast(short)((year - 1) * -1);
4140     }
4141
4142     ///
4143     @safe unittest
4144     {
4145         auto date = Date(2010, 1, 1);
4146         date.yearBC = 1;
4147         assert(date == Date(0, 1, 1));
4148
4149         date.yearBC = 10;
4150         assert(date == Date(-9, 1, 1));
4151     }
4152
4153     @safe unittest
4154     {
4155         assertThrown!DateTimeException((Date date){date.yearBC = -1;}(Date(1, 1, 1)));
4156
4157         auto date = Date(0, 7, 6);
4158         const cdate = Date(0, 7, 6);
4159         immutable idate = Date(0, 7, 6);
4160         date.yearBC = 7;
4161         assert(date.yearBC == 7);
4162         static assert(!__traits(compiles, cdate.yearBC = 7));
4163         static assert(!__traits(compiles, idate.yearBC = 7));
4164     }
4165
4166
4167     /++
4168         Month of a Gregorian Year.
4169      +/
4170     @property Month month() const @safe pure nothrow @nogc
4171     {
4172         return _month;
4173     }
4174
4175     ///
4176     @safe unittest
4177     {
4178         assert(Date(1999, 7, 6).month == 7);
4179         assert(Date(2010, 10, 4).month == 10);
4180         assert(Date(-7, 4, 5).month == 4);
4181     }
4182
4183     @safe unittest
4184     {
4185         assert(Date.init.month == 1);
4186         assert(Date(1999, 7, 6).month == 7);
4187         assert(Date(-1999, 7, 6).month == 7);
4188
4189         const cdate = Date(1999, 7, 6);
4190         immutable idate = Date(1999, 7, 6);
4191         assert(cdate.month == 7);
4192         assert(idate.month == 7);
4193     }
4194
4195     /++
4196         Month of a Gregorian Year.
4197
4198         Params:
4199             month = The month to set this $(LREF Date)'s month to.
4200
4201         Throws:
4202             $(REF DateTimeException,std,datetime,date) if the given month is
4203             not a valid month or if the current day would not be valid in the
4204             given month.
4205      +/
4206     @property void month(Month month) @safe pure
4207     {
4208         enforceValid!"months"(month);
4209         enforceValid!"days"(_year, month, _day);
4210         _month = cast(Month) month;
4211     }
4212
4213     @safe unittest
4214     {
4215         static void testDate(Date date, Month month, in Date expected = Date.init)
4216         {
4217             date.month = month;
4218             assert(expected != Date.init);
4219             assert(date == expected);
4220         }
4221
4222         assertThrown!DateTimeException(testDate(Date(1, 1, 1), cast(Month) 0));
4223         assertThrown!DateTimeException(testDate(Date(1, 1, 1), cast(Month) 13));
4224         assertThrown!DateTimeException(testDate(Date(1, 1, 29), cast(Month) 2));
4225         assertThrown!DateTimeException(testDate(Date(0, 1, 30), cast(Month) 2));
4226
4227         testDate(Date(1, 1, 1), cast(Month) 7, Date(1, 7, 1));
4228         testDate(Date(-1, 1, 1), cast(Month) 7, Date(-1, 7, 1));
4229
4230         const cdate = Date(1999, 7, 6);
4231         immutable idate = Date(1999, 7, 6);
4232         static assert(!__traits(compiles, cdate.month = 7));
4233         static assert(!__traits(compiles, idate.month = 7));
4234     }
4235
4236
4237     /++
4238         Day of a Gregorian Month.
4239      +/
4240     @property ubyte day() const @safe pure nothrow @nogc
4241     {
4242         return _day;
4243     }
4244
4245     ///
4246     @safe unittest
4247     {
4248         assert(Date(1999, 7, 6).day == 6);
4249         assert(Date(2010, 10, 4).day == 4);
4250         assert(Date(-7, 4, 5).day == 5);
4251     }
4252
4253     @safe unittest
4254     {
4255         import std.format : format;
4256         import std.range : chain;
4257
4258         static void test(Date date, int expected)
4259         {
4260             assert(date.day == expected, format("Value given: %s", date));
4261         }
4262
4263         foreach (year; chain(testYearsBC, testYearsAD))
4264         {
4265             foreach (md; testMonthDays)
4266                 test(Date(year, md.month, md.day), md.day);
4267         }
4268
4269         const cdate = Date(1999, 7, 6);
4270         immutable idate = Date(1999, 7, 6);
4271         assert(cdate.day == 6);
4272         assert(idate.day == 6);
4273     }
4274
4275     /++
4276         Day of a Gregorian Month.
4277
4278         Params:
4279             day = The day of the month to set this $(LREF Date)'s day to.
4280
4281         Throws:
4282             $(REF DateTimeException,std,datetime,date) if the given day is not
4283             a valid day of the current month.
4284      +/
4285     @property void day(int day) @safe pure
4286     {
4287         enforceValid!"days"(_year, _month, day);
4288         _day = cast(ubyte) day;
4289     }
4290
4291     @safe unittest
4292     {
4293         import std.exception : assertNotThrown;
4294
4295         static void testDate(Date date, int day)
4296         {
4297             date.day = day;
4298         }
4299
4300         // Test A.D.
4301         assertThrown!DateTimeException(testDate(Date(1, 1, 1), 0));
4302         assertThrown!DateTimeException(testDate(Date(1, 1, 1), 32));
4303         assertThrown!DateTimeException(testDate(Date(1, 2, 1), 29));
4304         assertThrown!DateTimeException(testDate(Date(4, 2, 1), 30));
4305         assertThrown!DateTimeException(testDate(Date(1, 3, 1), 32));
4306         assertThrown!DateTimeException(testDate(Date(1, 4, 1), 31));
4307         assertThrown!DateTimeException(testDate(Date(1, 5, 1), 32));
4308         assertThrown!DateTimeException(testDate(Date(1, 6, 1), 31));
4309         assertThrown!DateTimeException(testDate(Date(1, 7, 1), 32));
4310         assertThrown!DateTimeException(testDate(Date(1, 8, 1), 32));
4311         assertThrown!DateTimeException(testDate(Date(1, 9, 1), 31));
4312         assertThrown!DateTimeException(testDate(Date(1, 10, 1), 32));
4313         assertThrown!DateTimeException(testDate(Date(1, 11, 1), 31));
4314         assertThrown!DateTimeException(testDate(Date(1, 12, 1), 32));
4315
4316         assertNotThrown!DateTimeException(testDate(Date(1, 1, 1), 31));
4317         assertNotThrown!DateTimeException(testDate(Date(1, 2, 1), 28));
4318         assertNotThrown!DateTimeException(testDate(Date(4, 2, 1), 29));
4319         assertNotThrown!DateTimeException(testDate(Date(1, 3, 1), 31));
4320         assertNotThrown!DateTimeException(testDate(Date(1, 4, 1), 30));
4321         assertNotThrown!DateTimeException(testDate(Date(1, 5, 1), 31));
4322         assertNotThrown!DateTimeException(testDate(Date(1, 6, 1), 30));
4323         assertNotThrown!DateTimeException(testDate(Date(1, 7, 1), 31));
4324         assertNotThrown!DateTimeException(testDate(Date(1, 8, 1), 31));
4325         assertNotThrown!DateTimeException(testDate(Date(1, 9, 1), 30));
4326         assertNotThrown!DateTimeException(testDate(Date(1, 10, 1), 31));
4327         assertNotThrown!DateTimeException(testDate(Date(1, 11, 1), 30));
4328         assertNotThrown!DateTimeException(testDate(Date(1, 12, 1), 31));
4329
4330         {
4331             auto date = Date(1, 1, 1);
4332             date.day = 6;
4333             assert(date == Date(1, 1, 6));
4334         }
4335
4336         // Test B.C.
4337         assertThrown!DateTimeException(testDate(Date(-1, 1, 1), 0));
4338         assertThrown!DateTimeException(testDate(Date(-1, 1, 1), 32));
4339         assertThrown!DateTimeException(testDate(Date(-1, 2, 1), 29));
4340         assertThrown!DateTimeException(testDate(Date(0, 2, 1), 30));
4341         assertThrown!DateTimeException(testDate(Date(-1, 3, 1), 32));
4342         assertThrown!DateTimeException(testDate(Date(-1, 4, 1), 31));
4343         assertThrown!DateTimeException(testDate(Date(-1, 5, 1), 32));
4344         assertThrown!DateTimeException(testDate(Date(-1, 6, 1), 31));
4345         assertThrown!DateTimeException(testDate(Date(-1, 7, 1), 32));
4346         assertThrown!DateTimeException(testDate(Date(-1, 8, 1), 32));
4347         assertThrown!DateTimeException(testDate(Date(-1, 9, 1), 31));
4348         assertThrown!DateTimeException(testDate(Date(-1, 10, 1), 32));
4349         assertThrown!DateTimeException(testDate(Date(-1, 11, 1), 31));
4350         assertThrown!DateTimeException(testDate(Date(-1, 12, 1), 32));
4351
4352         assertNotThrown!DateTimeException(testDate(Date(-1, 1, 1), 31));
4353         assertNotThrown!DateTimeException(testDate(Date(-1, 2, 1), 28));
4354         assertNotThrown!DateTimeException(testDate(Date(0, 2, 1), 29));
4355         assertNotThrown!DateTimeException(testDate(Date(-1, 3, 1), 31));
4356         assertNotThrown!DateTimeException(testDate(Date(-1, 4, 1), 30));
4357         assertNotThrown!DateTimeException(testDate(Date(-1, 5, 1), 31));
4358         assertNotThrown!DateTimeException(testDate(Date(-1, 6, 1), 30));
4359         assertNotThrown!DateTimeException(testDate(Date(-1, 7, 1), 31));
4360         assertNotThrown!DateTimeException(testDate(Date(-1, 8, 1), 31));
4361         assertNotThrown!DateTimeException(testDate(Date(-1, 9, 1), 30));
4362         assertNotThrown!DateTimeException(testDate(Date(-1, 10, 1), 31));
4363         assertNotThrown!DateTimeException(testDate(Date(-1, 11, 1), 30));
4364         assertNotThrown!DateTimeException(testDate(Date(-1, 12, 1), 31));
4365
4366         {
4367             auto date = Date(-1, 1, 1);
4368             date.day = 6;
4369             assert(date == Date(-1, 1, 6));
4370         }
4371
4372         const cdate = Date(1999, 7, 6);
4373         immutable idate = Date(1999, 7, 6);
4374         static assert(!__traits(compiles, cdate.day = 6));
4375         static assert(!__traits(compiles, idate.day = 6));
4376     }
4377
4378
4379     /++
4380         Adds the given number of years or months to this $(LREF Date). A
4381         negative number will subtract.
4382
4383         Note that if day overflow is allowed, and the date with the adjusted
4384         year/month overflows the number of days in the new month, then the month
4385         will be incremented by one, and the day set to the number of days
4386         overflowed. (e.g. if the day were 31 and the new month were June, then
4387         the month would be incremented to July, and the new day would be 1). If
4388         day overflow is not allowed, then the day will be set to the last valid
4389         day in the month (e.g. June 31st would become June 30th).
4390
4391         Params:
4392             units         = The type of units to add ("years" or "months").
4393             value         = The number of months or years to add to this
4394                             $(LREF Date).
4395             allowOverflow = Whether the day should be allowed to overflow,
4396                             causing the month to increment.
4397       +/
4398     @safe pure nothrow @nogc
4399     ref Date add(string units)(long value, AllowDayOverflow allowOverflow = AllowDayOverflow.yes)
4400         if (units == "years")
4401     {
4402         _year += value;
4403
4404         if (_month == Month.feb && _day == 29 && !yearIsLeapYear(_year))
4405         {
4406             if (allowOverflow == AllowDayOverflow.yes)
4407             {
4408                 _month = Month.mar;
4409                 _day = 1;
4410             }
4411             else
4412                 _day = 28;
4413         }
4414
4415         return this;
4416     }
4417
4418     ///
4419     @safe unittest
4420     {
4421         auto d1 = Date(2010, 1, 1);
4422         d1.add!"months"(11);
4423         assert(d1 == Date(2010, 12, 1));
4424
4425         auto d2 = Date(2010, 1, 1);
4426         d2.add!"months"(-11);
4427         assert(d2 == Date(2009, 2, 1));
4428
4429         auto d3 = Date(2000, 2, 29);
4430         d3.add!"years"(1);
4431         assert(d3 == Date(2001, 3, 1));
4432
4433         auto d4 = Date(2000, 2, 29);
4434         d4.add!"years"(1, AllowDayOverflow.no);
4435         assert(d4 == Date(2001, 2, 28));
4436     }
4437
4438     // Test add!"years"() with AllowDayOverflow.yes
4439     @safe unittest
4440     {
4441         // Test A.D.
4442         {
4443             auto date = Date(1999, 7, 6);
4444             date.add!"years"(7);
4445             assert(date == Date(2006, 7, 6));
4446             date.add!"years"(-9);
4447             assert(date == Date(1997, 7, 6));
4448         }
4449
4450         {
4451             auto date = Date(1999, 2, 28);
4452             date.add!"years"(1);
4453             assert(date == Date(2000, 2, 28));
4454         }
4455
4456         {
4457             auto date = Date(2000, 2, 29);
4458             date.add!"years"(-1);
4459             assert(date == Date(1999, 3, 1));
4460         }
4461
4462         // Test B.C.
4463         {
4464             auto date = Date(-1999, 7, 6);
4465             date.add!"years"(-7);
4466             assert(date == Date(-2006, 7, 6));
4467             date.add!"years"(9);
4468             assert(date == Date(-1997, 7, 6));
4469         }
4470
4471         {
4472             auto date = Date(-1999, 2, 28);
4473             date.add!"years"(-1);
4474             assert(date == Date(-2000, 2, 28));
4475         }
4476
4477         {
4478             auto date = Date(-2000, 2, 29);
4479             date.add!"years"(1);
4480             assert(date == Date(-1999, 3, 1));
4481         }
4482
4483         // Test Both
4484         {
4485             auto date = Date(4, 7, 6);
4486             date.add!"years"(-5);
4487             assert(date == Date(-1, 7, 6));
4488             date.add!"years"(5);
4489             assert(date == Date(4, 7, 6));
4490         }
4491
4492         {
4493             auto date = Date(-4, 7, 6);
4494             date.add!"years"(5);
4495             assert(date == Date(1, 7, 6));
4496             date.add!"years"(-5);
4497             assert(date == Date(-4, 7, 6));
4498         }
4499
4500         {
4501             auto date = Date(4, 7, 6);
4502             date.add!"years"(-8);
4503             assert(date == Date(-4, 7, 6));
4504             date.add!"years"(8);
4505             assert(date == Date(4, 7, 6));
4506         }
4507
4508         {
4509             auto date = Date(-4, 7, 6);
4510             date.add!"years"(8);
4511             assert(date == Date(4, 7, 6));
4512             date.add!"years"(-8);
4513             assert(date == Date(-4, 7, 6));
4514         }
4515
4516         {
4517             auto date = Date(-4, 2, 29);
4518             date.add!"years"(5);
4519             assert(date == Date(1, 3, 1));
4520         }
4521
4522         {
4523             auto date = Date(4, 2, 29);
4524             date.add!"years"(-5);
4525             assert(date == Date(-1, 3, 1));
4526         }
4527
4528         {
4529             auto date = Date(4, 2, 29);
4530             date.add!"years"(-5).add!"years"(7);
4531             assert(date == Date(6, 3, 1));
4532         }
4533
4534         const cdate = Date(1999, 7, 6);
4535         immutable idate = Date(1999, 7, 6);
4536         static assert(!__traits(compiles, cdate.add!"years"(7)));
4537         static assert(!__traits(compiles, idate.add!"years"(7)));
4538     }
4539
4540     // Test add!"years"() with AllowDayOverflow.no
4541     @safe unittest
4542     {
4543         // Test A.D.
4544         {
4545             auto date = Date(1999, 7, 6);
4546             date.add!"years"(7, AllowDayOverflow.no);
4547             assert(date == Date(2006, 7, 6));
4548             date.add!"years"(-9, AllowDayOverflow.no);
4549             assert(date == Date(1997, 7, 6));
4550         }
4551
4552         {
4553             auto date = Date(1999, 2, 28);
4554             date.add!"years"(1, AllowDayOverflow.no);
4555             assert(date == Date(2000, 2, 28));
4556         }
4557
4558         {
4559             auto date = Date(2000, 2, 29);
4560             date.add!"years"(-1, AllowDayOverflow.no);
4561             assert(date == Date(1999, 2, 28));
4562         }
4563
4564         // Test B.C.
4565         {
4566             auto date = Date(-1999, 7, 6);
4567             date.add!"years"(-7, AllowDayOverflow.no);
4568             assert(date == Date(-2006, 7, 6));
4569             date.add!"years"(9, AllowDayOverflow.no);
4570             assert(date == Date(-1997, 7, 6));
4571         }
4572
4573         {
4574             auto date = Date(-1999, 2, 28);
4575             date.add!"years"(-1, AllowDayOverflow.no);
4576             assert(date == Date(-2000, 2, 28));
4577         }
4578
4579         {
4580             auto date = Date(-2000, 2, 29);
4581             date.add!"years"(1, AllowDayOverflow.no);
4582             assert(date == Date(-1999, 2, 28));
4583         }
4584
4585         // Test Both
4586         {
4587             auto date = Date(4, 7, 6);
4588             date.add!"years"(-5, AllowDayOverflow.no);
4589             assert(date == Date(-1, 7, 6));
4590             date.add!"years"(5, AllowDayOverflow.no);
4591             assert(date == Date(4, 7, 6));
4592         }
4593
4594         {
4595             auto date = Date(-4, 7, 6);
4596             date.add!"years"(5, AllowDayOverflow.no);
4597             assert(date == Date(1, 7, 6));
4598             date.add!"years"(-5, AllowDayOverflow.no);
4599             assert(date == Date(-4, 7, 6));
4600         }
4601
4602         {
4603             auto date = Date(4, 7, 6);
4604             date.add!"years"(-8, AllowDayOverflow.no);
4605             assert(date == Date(-4, 7, 6));
4606             date.add!"years"(8, AllowDayOverflow.no);
4607             assert(date == Date(4, 7, 6));
4608         }
4609
4610         {
4611             auto date = Date(-4, 7, 6);
4612             date.add!"years"(8, AllowDayOverflow.no);
4613             assert(date == Date(4, 7, 6));
4614             date.add!"years"(-8, AllowDayOverflow.no);
4615             assert(date == Date(-4, 7, 6));
4616         }
4617
4618         {
4619             auto date = Date(-4, 2, 29);
4620             date.add!"years"(5, AllowDayOverflow.no);
4621             assert(date == Date(1, 2, 28));
4622         }
4623
4624         {
4625             auto date = Date(4, 2, 29);
4626             date.add!"years"(-5, AllowDayOverflow.no);
4627             assert(date == Date(-1, 2, 28));
4628         }
4629
4630         {
4631             auto date = Date(4, 2, 29);
4632             date.add!"years"(-5, AllowDayOverflow.no).add!"years"(7, AllowDayOverflow.no);
4633             assert(date == Date(6, 2, 28));
4634         }
4635     }
4636
4637
4638     // Shares documentation with "years" version.
4639     @safe pure nothrow @nogc
4640     ref Date add(string units)(long months, AllowDayOverflow allowOverflow = AllowDayOverflow.yes)
4641         if (units == "months")
4642     {
4643         auto years = months / 12;
4644         months %= 12;
4645         auto newMonth = _month + months;
4646
4647         if (months < 0)
4648         {
4649             if (newMonth < 1)
4650             {
4651                 newMonth += 12;
4652                 --years;
4653             }
4654         }
4655         else if (newMonth > 12)
4656         {
4657             newMonth -= 12;
4658             ++years;
4659         }
4660
4661         _year += years;
4662         _month = cast(Month) newMonth;
4663
4664         immutable currMaxDay = maxDay(_year, _month);
4665         immutable overflow = _day - currMaxDay;
4666
4667         if (overflow > 0)
4668         {
4669             if (allowOverflow == AllowDayOverflow.yes)
4670             {
4671                 ++_month;
4672                 _day = cast(ubyte) overflow;
4673             }
4674             else
4675                 _day = cast(ubyte) currMaxDay;
4676         }
4677
4678         return this;
4679     }
4680
4681     // Test add!"months"() with AllowDayOverflow.yes
4682     @safe unittest
4683     {
4684         // Test A.D.
4685         {
4686             auto date = Date(1999, 7, 6);
4687             date.add!"months"(3);
4688             assert(date == Date(1999, 10, 6));
4689             date.add!"months"(-4);
4690             assert(date == Date(1999, 6, 6));
4691         }
4692
4693         {
4694             auto date = Date(1999, 7, 6);
4695             date.add!"months"(6);
4696             assert(date == Date(2000, 1, 6));
4697             date.add!"months"(-6);
4698             assert(date == Date(1999, 7, 6));
4699         }
4700
4701         {
4702             auto date = Date(1999, 7, 6);
4703             date.add!"months"(27);
4704             assert(date == Date(2001, 10, 6));
4705             date.add!"months"(-28);
4706             assert(date == Date(1999, 6, 6));
4707         }
4708
4709         {
4710             auto date = Date(1999, 5, 31);
4711             date.add!"months"(1);
4712             assert(date == Date(1999, 7, 1));
4713         }
4714
4715         {
4716             auto date = Date(1999, 5, 31);
4717             date.add!"months"(-1);
4718             assert(date == Date(1999, 5, 1));
4719         }
4720
4721         {
4722             auto date = Date(1999, 2, 28);
4723             date.add!"months"(12);
4724             assert(date == Date(2000, 2, 28));
4725         }
4726
4727         {
4728             auto date = Date(2000, 2, 29);
4729             date.add!"months"(12);
4730             assert(date == Date(2001, 3, 1));
4731         }
4732
4733         {
4734             auto date = Date(1999, 7, 31);
4735             date.add!"months"(1);
4736             assert(date == Date(1999, 8, 31));
4737             date.add!"months"(1);
4738             assert(date == Date(1999, 10, 1));
4739         }
4740
4741         {
4742             auto date = Date(1998, 8, 31);
4743             date.add!"months"(13);
4744             assert(date == Date(1999, 10, 1));
4745             date.add!"months"(-13);
4746             assert(date == Date(1998, 9, 1));
4747         }
4748
4749         {
4750             auto date = Date(1997, 12, 31);
4751             date.add!"months"(13);
4752             assert(date == Date(1999, 1, 31));
4753             date.add!"months"(-13);
4754             assert(date == Date(1997, 12, 31));
4755         }
4756
4757         {
4758             auto date = Date(1997, 12, 31);
4759             date.add!"months"(14);
4760             assert(date == Date(1999, 3, 3));
4761             date.add!"months"(-14);
4762             assert(date == Date(1998, 1, 3));
4763         }
4764
4765         {
4766             auto date = Date(1998, 12, 31);
4767             date.add!"months"(14);
4768             assert(date == Date(2000, 3, 2));
4769             date.add!"months"(-14);
4770             assert(date == Date(1999, 1, 2));
4771         }
4772
4773         {
4774             auto date = Date(1999, 12, 31);
4775             date.add!"months"(14);
4776             assert(date == Date(2001, 3, 3));
4777             date.add!"months"(-14);
4778             assert(date == Date(2000, 1, 3));
4779         }
4780
4781         // Test B.C.
4782         {
4783             auto date = Date(-1999, 7, 6);
4784             date.add!"months"(3);
4785             assert(date == Date(-1999, 10, 6));
4786             date.add!"months"(-4);
4787             assert(date == Date(-1999, 6, 6));
4788         }
4789
4790         {
4791             auto date = Date(-1999, 7, 6);
4792             date.add!"months"(6);
4793             assert(date == Date(-1998, 1, 6));
4794             date.add!"months"(-6);
4795             assert(date == Date(-1999, 7, 6));
4796         }
4797
4798         {
4799             auto date = Date(-1999, 7, 6);
4800             date.add!"months"(-27);
4801             assert(date == Date(-2001, 4, 6));
4802             date.add!"months"(28);
4803             assert(date == Date(-1999, 8, 6));
4804         }
4805
4806         {
4807             auto date = Date(-1999, 5, 31);
4808             date.add!"months"(1);
4809             assert(date == Date(-1999, 7, 1));
4810         }
4811
4812         {
4813             auto date = Date(-1999, 5, 31);
4814             date.add!"months"(-1);
4815             assert(date == Date(-1999, 5, 1));
4816         }
4817
4818         {
4819             auto date = Date(-1999, 2, 28);
4820             date.add!"months"(-12);
4821             assert(date == Date(-2000, 2, 28));
4822         }
4823
4824         {
4825             auto date = Date(-2000, 2, 29);
4826             date.add!"months"(-12);
4827             assert(date == Date(-2001, 3, 1));
4828         }
4829
4830         {
4831             auto date = Date(-1999, 7, 31);
4832             date.add!"months"(1);
4833             assert(date == Date(-1999, 8, 31));
4834             date.add!"months"(1);
4835             assert(date == Date(-1999, 10, 1));
4836         }
4837
4838         {
4839             auto date = Date(-1998, 8, 31);
4840             date.add!"months"(13);
4841             assert(date == Date(-1997, 10, 1));
4842             date.add!"months"(-13);
4843             assert(date == Date(-1998, 9, 1));
4844         }
4845
4846         {
4847             auto date = Date(-1997, 12, 31);
4848             date.add!"months"(13);
4849             assert(date == Date(-1995, 1, 31));
4850             date.add!"months"(-13);
4851             assert(date == Date(-1997, 12, 31));
4852         }
4853
4854         {
4855             auto date = Date(-1997, 12, 31);
4856             date.add!"months"(14);
4857             assert(date == Date(-1995, 3, 3));
4858             date.add!"months"(-14);
4859             assert(date == Date(-1996, 1, 3));
4860         }
4861
4862         {
4863             auto date = Date(-2002, 12, 31);
4864             date.add!"months"(14);
4865             assert(date == Date(-2000, 3, 2));
4866             date.add!"months"(-14);
4867             assert(date == Date(-2001, 1, 2));
4868         }
4869
4870         {
4871             auto date = Date(-2001, 12, 31);
4872             date.add!"months"(14);
4873             assert(date == Date(-1999, 3, 3));
4874             date.add!"months"(-14);
4875             assert(date == Date(-2000, 1, 3));
4876         }
4877
4878         // Test Both
4879         {
4880             auto date = Date(1, 1, 1);
4881             date.add!"months"(-1);
4882             assert(date == Date(0, 12, 1));
4883             date.add!"months"(1);
4884             assert(date == Date(1, 1, 1));
4885         }
4886
4887         {
4888             auto date = Date(4, 1, 1);
4889             date.add!"months"(-48);
4890             assert(date == Date(0, 1, 1));
4891             date.add!"months"(48);
4892             assert(date == Date(4, 1, 1));
4893         }
4894
4895         {
4896             auto date = Date(4, 3, 31);
4897             date.add!"months"(-49);
4898             assert(date == Date(0, 3, 2));
4899             date.add!"months"(49);
4900             assert(date == Date(4, 4, 2));
4901         }
4902
4903         {
4904             auto date = Date(4, 3, 31);
4905             date.add!"months"(-85);
4906             assert(date == Date(-3, 3, 3));
4907             date.add!"months"(85);
4908             assert(date == Date(4, 4, 3));
4909         }
4910
4911         {
4912             auto date = Date(-3, 3, 31);
4913             date.add!"months"(85).add!"months"(-83);
4914             assert(date == Date(-3, 6, 1));
4915         }
4916
4917         const cdate = Date(1999, 7, 6);
4918         immutable idate = Date(1999, 7, 6);
4919         static assert(!__traits(compiles, cdate.add!"months"(3)));
4920         static assert(!__traits(compiles, idate.add!"months"(3)));
4921     }
4922
4923     // Test add!"months"() with AllowDayOverflow.no
4924     @safe unittest
4925     {
4926         // Test A.D.
4927         {
4928             auto date = Date(1999, 7, 6);
4929             date.add!"months"(3, AllowDayOverflow.no);
4930             assert(date == Date(1999, 10, 6));
4931             date.add!"months"(-4, AllowDayOverflow.no);
4932             assert(date == Date(1999, 6, 6));
4933         }
4934
4935         {
4936             auto date = Date(1999, 7, 6);
4937             date.add!"months"(6, AllowDayOverflow.no);
4938             assert(date == Date(2000, 1, 6));
4939             date.add!"months"(-6, AllowDayOverflow.no);
4940             assert(date == Date(1999, 7, 6));
4941         }
4942
4943         {
4944             auto date = Date(1999, 7, 6);
4945             date.add!"months"(27, AllowDayOverflow.no);
4946             assert(date == Date(2001, 10, 6));
4947             date.add!"months"(-28, AllowDayOverflow.no);
4948             assert(date == Date(1999, 6, 6));
4949         }
4950
4951         {
4952             auto date = Date(1999, 5, 31);
4953             date.add!"months"(1, AllowDayOverflow.no);
4954             assert(date == Date(1999, 6, 30));
4955         }
4956
4957         {
4958             auto date = Date(1999, 5, 31);
4959             date.add!"months"(-1, AllowDayOverflow.no);
4960             assert(date == Date(1999, 4, 30));
4961         }
4962
4963         {
4964             auto date = Date(1999, 2, 28);
4965             date.add!"months"(12, AllowDayOverflow.no);
4966             assert(date == Date(2000, 2, 28));
4967         }
4968
4969         {
4970             auto date = Date(2000, 2, 29);
4971             date.add!"months"(12, AllowDayOverflow.no);
4972             assert(date == Date(2001, 2, 28));
4973         }
4974
4975         {
4976             auto date = Date(1999, 7, 31);
4977             date.add!"months"(1, AllowDayOverflow.no);
4978             assert(date == Date(1999, 8, 31));
4979             date.add!"months"(1, AllowDayOverflow.no);
4980             assert(date == Date(1999, 9, 30));
4981         }
4982
4983         {
4984             auto date = Date(1998, 8, 31);
4985             date.add!"months"(13, AllowDayOverflow.no);
4986             assert(date == Date(1999, 9, 30));
4987             date.add!"months"(-13, AllowDayOverflow.no);
4988             assert(date == Date(1998, 8, 30));
4989         }
4990
4991         {
4992             auto date = Date(1997, 12, 31);
4993             date.add!"months"(13, AllowDayOverflow.no);
4994             assert(date == Date(1999, 1, 31));
4995             date.add!"months"(-13, AllowDayOverflow.no);
4996             assert(date == Date(1997, 12, 31));
4997         }
4998
4999         {
5000             auto date = Date(1997, 12, 31);
5001             date.add!"months"(14, AllowDayOverflow.no);
5002             assert(date == Date(1999, 2, 28));
5003             date.add!"months"(-14, AllowDayOverflow.no);
5004             assert(date == Date(1997, 12, 28));
5005         }
5006
5007         {
5008             auto date = Date(1998, 12, 31);
5009             date.add!"months"(14, AllowDayOverflow.no);
5010             assert(date == Date(2000, 2, 29));
5011             date.add!"months"(-14, AllowDayOverflow.no);
5012             assert(date == Date(1998, 12, 29));
5013         }
5014
5015         {
5016             auto date = Date(1999, 12, 31);
5017             date.add!"months"(14, AllowDayOverflow.no);
5018             assert(date == Date(2001, 2, 28));
5019             date.add!"months"(-14, AllowDayOverflow.no);
5020             assert(date == Date(1999, 12, 28));
5021         }
5022
5023         // Test B.C.
5024         {
5025             auto date = Date(-1999, 7, 6);
5026             date.add!"months"(3, AllowDayOverflow.no);
5027             assert(date == Date(-1999, 10, 6));
5028             date.add!"months"(-4, AllowDayOverflow.no);
5029             assert(date == Date(-1999, 6, 6));
5030         }
5031
5032         {
5033             auto date = Date(-1999, 7, 6);
5034             date.add!"months"(6, AllowDayOverflow.no);
5035             assert(date == Date(-1998, 1, 6));
5036             date.add!"months"(-6, AllowDayOverflow.no);
5037             assert(date == Date(-1999, 7, 6));
5038         }
5039
5040         {
5041             auto date = Date(-1999, 7, 6);
5042             date.add!"months"(-27, AllowDayOverflow.no);
5043             assert(date == Date(-2001, 4, 6));
5044             date.add!"months"(28, AllowDayOverflow.no);
5045             assert(date == Date(-1999, 8, 6));
5046         }
5047
5048         {
5049             auto date = Date(-1999, 5, 31);
5050             date.add!"months"(1, AllowDayOverflow.no);
5051             assert(date == Date(-1999, 6, 30));
5052         }
5053
5054         {
5055             auto date = Date(-1999, 5, 31);
5056             date.add!"months"(-1, AllowDayOverflow.no);
5057             assert(date == Date(-1999, 4, 30));
5058         }
5059
5060         {
5061             auto date = Date(-1999, 2, 28);
5062             date.add!"months"(-12, AllowDayOverflow.no);
5063             assert(date == Date(-2000, 2, 28));
5064         }
5065
5066         {
5067             auto date = Date(-2000, 2, 29);
5068             date.add!"months"(-12, AllowDayOverflow.no);
5069             assert(date == Date(-2001, 2, 28));
5070         }
5071
5072         {
5073             auto date = Date(-1999, 7, 31);
5074             date.add!"months"(1, AllowDayOverflow.no);
5075             assert(date == Date(-1999, 8, 31));
5076             date.add!"months"(1, AllowDayOverflow.no);
5077             assert(date == Date(-1999, 9, 30));
5078         }
5079
5080         {
5081             auto date = Date(-1998, 8, 31);
5082             date.add!"months"(13, AllowDayOverflow.no);
5083             assert(date == Date(-1997, 9, 30));
5084             date.add!"months"(-13, AllowDayOverflow.no);
5085             assert(date == Date(-1998, 8, 30));
5086         }
5087
5088         {
5089             auto date = Date(-1997, 12, 31);
5090             date.add!"months"(13, AllowDayOverflow.no);
5091             assert(date == Date(-1995, 1, 31));
5092             date.add!"months"(-13, AllowDayOverflow.no);
5093             assert(date == Date(-1997, 12, 31));
5094         }
5095
5096         {
5097             auto date = Date(-1997, 12, 31);
5098             date.add!"months"(14, AllowDayOverflow.no);
5099             assert(date == Date(-1995, 2, 28));
5100             date.add!"months"(-14, AllowDayOverflow.no);
5101             assert(date == Date(-1997, 12, 28));
5102         }
5103
5104         {
5105             auto date = Date(-2002, 12, 31);
5106             date.add!"months"(14, AllowDayOverflow.no);
5107             assert(date == Date(-2000, 2, 29));
5108             date.add!"months"(-14, AllowDayOverflow.no);
5109             assert(date == Date(-2002, 12, 29));
5110         }
5111
5112         {
5113             auto date = Date(-2001, 12, 31);
5114             date.add!"months"(14, AllowDayOverflow.no);
5115             assert(date == Date(-1999, 2, 28));
5116             date.add!"months"(-14, AllowDayOverflow.no);
5117             assert(date == Date(-2001, 12, 28));
5118         }
5119
5120         // Test Both
5121         {
5122             auto date = Date(1, 1, 1);
5123             date.add!"months"(-1, AllowDayOverflow.no);
5124             assert(date == Date(0, 12, 1));
5125             date.add!"months"(1, AllowDayOverflow.no);
5126             assert(date == Date(1, 1, 1));
5127         }
5128
5129         {
5130             auto date = Date(4, 1, 1);
5131             date.add!"months"(-48, AllowDayOverflow.no);
5132             assert(date == Date(0, 1, 1));
5133             date.add!"months"(48, AllowDayOverflow.no);
5134             assert(date == Date(4, 1, 1));
5135         }
5136
5137         {
5138             auto date = Date(4, 3, 31);
5139             date.add!"months"(-49, AllowDayOverflow.no);
5140             assert(date == Date(0, 2, 29));
5141             date.add!"months"(49, AllowDayOverflow.no);
5142             assert(date == Date(4, 3, 29));
5143         }
5144
5145         {
5146             auto date = Date(4, 3, 31);
5147             date.add!"months"(-85, AllowDayOverflow.no);
5148             assert(date == Date(-3, 2, 28));
5149             date.add!"months"(85, AllowDayOverflow.no);
5150             assert(date == Date(4, 3, 28));
5151         }
5152
5153         {
5154             auto date = Date(-3, 3, 31);
5155             date.add!"months"(85, AllowDayOverflow.no).add!"months"(-83, AllowDayOverflow.no);
5156             assert(date == Date(-3, 5, 30));
5157         }
5158     }
5159
5160
5161     /++
5162         Adds the given number of years or months to this $(LREF Date). A negative
5163         number will subtract.
5164
5165         The difference between rolling and adding is that rolling does not
5166         affect larger units. Rolling a $(LREF Date) 12 months gets
5167         the exact same $(LREF Date). However, the days can still be affected due
5168         to the differing number of days in each month.
5169
5170         Because there are no units larger than years, there is no difference
5171         between adding and rolling years.
5172
5173         Params:
5174             units         = The type of units to add ("years" or "months").
5175             value         = The number of months or years to add to this
5176                             $(LREF Date).
5177             allowOverflow = Whether the day should be allowed to overflow,
5178                             causing the month to increment.
5179       +/
5180     @safe pure nothrow @nogc
5181     ref Date roll(string units)(long value, AllowDayOverflow allowOverflow = AllowDayOverflow.yes)
5182         if (units == "years")
5183     {
5184         return add!"years"(value, allowOverflow);
5185     }
5186
5187     ///
5188     @safe unittest
5189     {
5190         auto d1 = Date(2010, 1, 1);
5191         d1.roll!"months"(1);
5192         assert(d1 == Date(2010, 2, 1));
5193
5194         auto d2 = Date(2010, 1, 1);
5195         d2.roll!"months"(-1);
5196         assert(d2 == Date(2010, 12, 1));
5197
5198         auto d3 = Date(1999, 1, 29);
5199         d3.roll!"months"(1);
5200         assert(d3 == Date(1999, 3, 1));
5201
5202         auto d4 = Date(1999, 1, 29);
5203         d4.roll!"months"(1, AllowDayOverflow.no);
5204         assert(d4 == Date(1999, 2, 28));
5205
5206         auto d5 = Date(2000, 2, 29);
5207         d5.roll!"years"(1);
5208         assert(d5 == Date(2001, 3, 1));
5209
5210         auto d6 = Date(2000, 2, 29);
5211         d6.roll!"years"(1, AllowDayOverflow.no);
5212         assert(d6 == Date(2001, 2, 28));
5213     }
5214
5215     @safe unittest
5216     {
5217         const cdate = Date(1999, 7, 6);
5218         immutable idate = Date(1999, 7, 6);
5219         static assert(!__traits(compiles, cdate.roll!"years"(3)));
5220         static assert(!__traits(compiles, idate.rolYears(3)));
5221     }
5222
5223
5224     // Shares documentation with "years" version.
5225     @safe pure nothrow @nogc
5226     ref Date roll(string units)(long months, AllowDayOverflow allowOverflow = AllowDayOverflow.yes)
5227         if (units == "months")
5228     {
5229         months %= 12;
5230         auto newMonth = _month + months;
5231
5232         if (months < 0)
5233         {
5234             if (newMonth < 1)
5235                 newMonth += 12;
5236         }
5237         else
5238         {
5239             if (newMonth > 12)
5240                 newMonth -= 12;
5241         }
5242
5243         _month = cast(Month) newMonth;
5244
5245         immutable currMaxDay = maxDay(_year, _month);
5246         immutable overflow = _day - currMaxDay;
5247
5248         if (overflow > 0)
5249         {
5250             if (allowOverflow == AllowDayOverflow.yes)
5251             {
5252                 ++_month;
5253                 _day = cast(ubyte) overflow;
5254             }
5255             else
5256                 _day = cast(ubyte) currMaxDay;
5257         }
5258
5259         return this;
5260     }
5261
5262     // Test roll!"months"() with AllowDayOverflow.yes
5263     @safe unittest
5264     {
5265         // Test A.D.
5266         {
5267             auto date = Date(1999, 7, 6);
5268             date.roll!"months"(3);
5269             assert(date == Date(1999, 10, 6));
5270             date.roll!"months"(-4);
5271             assert(date == Date(1999, 6, 6));
5272         }
5273
5274         {
5275             auto date = Date(1999, 7, 6);
5276             date.roll!"months"(6);
5277             assert(date == Date(1999, 1, 6));
5278             date.roll!"months"(-6);
5279             assert(date == Date(1999, 7, 6));
5280         }
5281
5282         {
5283             auto date = Date(1999, 7, 6);
5284             date.roll!"months"(27);
5285             assert(date == Date(1999, 10, 6));
5286             date.roll!"months"(-28);
5287             assert(date == Date(1999, 6, 6));
5288         }
5289
5290         {
5291             auto date = Date(1999, 5, 31);
5292             date.roll!"months"(1);
5293             assert(date == Date(1999, 7, 1));
5294         }
5295
5296         {
5297             auto date = Date(1999, 5, 31);
5298             date.roll!"months"(-1);
5299             assert(date == Date(1999, 5, 1));
5300         }
5301
5302         {
5303             auto date = Date(1999, 2, 28);
5304             date.roll!"months"(12);
5305             assert(date == Date(1999, 2, 28));
5306         }
5307
5308         {
5309             auto date = Date(2000, 2, 29);
5310             date.roll!"months"(12);
5311             assert(date == Date(2000, 2, 29));
5312         }
5313
5314         {
5315             auto date = Date(1999, 7, 31);
5316             date.roll!"months"(1);
5317             assert(date == Date(1999, 8, 31));
5318             date.roll!"months"(1);
5319             assert(date == Date(1999, 10, 1));
5320         }
5321
5322         {
5323             auto date = Date(1998, 8, 31);
5324             date.roll!"months"(13);
5325             assert(date == Date(1998, 10, 1));
5326             date.roll!"months"(-13);
5327             assert(date == Date(1998, 9, 1));
5328         }
5329
5330         {
5331             auto date = Date(1997, 12, 31);
5332             date.roll!"months"(13);
5333             assert(date == Date(1997, 1, 31));
5334             date.roll!"months"(-13);
5335             assert(date == Date(1997, 12, 31));
5336         }
5337
5338         {
5339             auto date = Date(1997, 12, 31);
5340             date.roll!"months"(14);
5341             assert(date == Date(1997, 3, 3));
5342             date.roll!"months"(-14);
5343             assert(date == Date(1997, 1, 3));
5344         }
5345
5346         {
5347             auto date = Date(1998, 12, 31);
5348             date.roll!"months"(14);
5349             assert(date == Date(1998, 3, 3));
5350             date.roll!"months"(-14);
5351             assert(date == Date(1998, 1, 3));
5352         }
5353
5354         {
5355             auto date = Date(1999, 12, 31);
5356             date.roll!"months"(14);
5357             assert(date == Date(1999, 3, 3));
5358             date.roll!"months"(-14);
5359             assert(date == Date(1999, 1, 3));
5360         }
5361
5362         // Test B.C.
5363         {
5364             auto date = Date(-1999, 7, 6);
5365             date.roll!"months"(3);
5366             assert(date == Date(-1999, 10, 6));
5367             date.roll!"months"(-4);
5368             assert(date == Date(-1999, 6, 6));
5369         }
5370
5371         {
5372             auto date = Date(-1999, 7, 6);
5373             date.roll!"months"(6);
5374             assert(date == Date(-1999, 1, 6));
5375             date.roll!"months"(-6);
5376             assert(date == Date(-1999, 7, 6));
5377         }
5378
5379         {
5380             auto date = Date(-1999, 7, 6);
5381             date.roll!"months"(-27);
5382             assert(date == Date(-1999, 4, 6));
5383             date.roll!"months"(28);
5384             assert(date == Date(-1999, 8, 6));
5385         }
5386
5387         {
5388             auto date = Date(-1999, 5, 31);
5389             date.roll!"months"(1);
5390             assert(date == Date(-1999, 7, 1));
5391         }
5392
5393         {
5394             auto date = Date(-1999, 5, 31);
5395             date.roll!"months"(-1);
5396             assert(date == Date(-1999, 5, 1));
5397         }
5398
5399         {
5400             auto date = Date(-1999, 2, 28);
5401             date.roll!"months"(-12);
5402             assert(date == Date(-1999, 2, 28));
5403         }
5404
5405         {
5406             auto date = Date(-2000, 2, 29);
5407             date.roll!"months"(-12);
5408             assert(date == Date(-2000, 2, 29));
5409         }
5410
5411         {
5412             auto date = Date(-1999, 7, 31);
5413             date.roll!"months"(1);
5414             assert(date == Date(-1999, 8, 31));
5415             date.roll!"months"(1);
5416             assert(date == Date(-1999, 10, 1));
5417         }
5418
5419         {
5420             auto date = Date(-1998, 8, 31);
5421             date.roll!"months"(13);
5422             assert(date == Date(-1998, 10, 1));
5423             date.roll!"months"(-13);
5424             assert(date == Date(-1998, 9, 1));
5425         }
5426
5427         {
5428             auto date = Date(-1997, 12, 31);
5429             date.roll!"months"(13);
5430             assert(date == Date(-1997, 1, 31));
5431             date.roll!"months"(-13);
5432             assert(date == Date(-1997, 12, 31));
5433         }
5434
5435         {
5436             auto date = Date(-1997, 12, 31);
5437             date.roll!"months"(14);
5438             assert(date == Date(-1997, 3, 3));
5439             date.roll!"months"(-14);
5440             assert(date == Date(-1997, 1, 3));
5441         }
5442
5443         {
5444             auto date = Date(-2002, 12, 31);
5445             date.roll!"months"(14);
5446             assert(date == Date(-2002, 3, 3));
5447             date.roll!"months"(-14);
5448             assert(date == Date(-2002, 1, 3));
5449         }
5450
5451         {
5452             auto date = Date(-2001, 12, 31);
5453             date.roll!"months"(14);
5454             assert(date == Date(-2001, 3, 3));
5455             date.roll!"months"(-14);
5456             assert(date == Date(-2001, 1, 3));
5457         }
5458
5459         // Test Both
5460         {
5461             auto date = Date(1, 1, 1);
5462             date.roll!"months"(-1);
5463             assert(date == Date(1, 12, 1));
5464             date.roll!"months"(1);
5465             assert(date == Date(1, 1, 1));
5466         }
5467
5468         {
5469             auto date = Date(4, 1, 1);
5470             date.roll!"months"(-48);
5471             assert(date == Date(4, 1, 1));
5472             date.roll!"months"(48);
5473             assert(date == Date(4, 1, 1));
5474         }
5475
5476         {
5477             auto date = Date(4, 3, 31);
5478             date.roll!"months"(-49);
5479             assert(date == Date(4, 3, 2));
5480             date.roll!"months"(49);
5481             assert(date == Date(4, 4, 2));
5482         }
5483
5484         {
5485             auto date = Date(4, 3, 31);
5486             date.roll!"months"(-85);
5487             assert(date == Date(4, 3, 2));
5488             date.roll!"months"(85);
5489             assert(date == Date(4, 4, 2));
5490         }
5491
5492         {
5493             auto date = Date(-1, 1, 1);
5494             date.roll!"months"(-1);
5495             assert(date == Date(-1, 12, 1));
5496             date.roll!"months"(1);
5497             assert(date == Date(-1, 1, 1));
5498         }
5499
5500         {
5501             auto date = Date(-4, 1, 1);
5502             date.roll!"months"(-48);
5503             assert(date == Date(-4, 1, 1));
5504             date.roll!"months"(48);
5505             assert(date == Date(-4, 1, 1));
5506         }
5507
5508         {
5509             auto date = Date(-4, 3, 31);
5510             date.roll!"months"(-49);
5511             assert(date == Date(-4, 3, 2));
5512             date.roll!"months"(49);
5513             assert(date == Date(-4, 4, 2));
5514         }
5515
5516         {
5517             auto date = Date(-4, 3, 31);
5518             date.roll!"months"(-85);
5519             assert(date == Date(-4, 3, 2));
5520             date.roll!"months"(85);
5521             assert(date == Date(-4, 4, 2));
5522         }
5523
5524         {
5525             auto date = Date(-3, 3, 31);
5526             date.roll!"months"(85).roll!"months"(-83);
5527             assert(date == Date(-3, 6, 1));
5528         }
5529
5530         const cdate = Date(1999, 7, 6);
5531         immutable idate = Date(1999, 7, 6);
5532         static assert(!__traits(compiles, cdate.roll!"months"(3)));
5533         static assert(!__traits(compiles, idate.roll!"months"(3)));
5534     }
5535
5536     // Test roll!"months"() with AllowDayOverflow.no
5537     @safe unittest
5538     {
5539         // Test A.D.
5540         {
5541             auto date = Date(1999, 7, 6);
5542             date.roll!"months"(3, AllowDayOverflow.no);
5543             assert(date == Date(1999, 10, 6));
5544             date.roll!"months"(-4, AllowDayOverflow.no);
5545             assert(date == Date(1999, 6, 6));
5546         }
5547
5548         {
5549             auto date = Date(1999, 7, 6);
5550             date.roll!"months"(6, AllowDayOverflow.no);
5551             assert(date == Date(1999, 1, 6));
5552             date.roll!"months"(-6, AllowDayOverflow.no);
5553             assert(date == Date(1999, 7, 6));
5554         }
5555
5556         {
5557             auto date = Date(1999, 7, 6);
5558             date.roll!"months"(27, AllowDayOverflow.no);
5559             assert(date == Date(1999, 10, 6));
5560             date.roll!"months"(-28, AllowDayOverflow.no);
5561             assert(date == Date(1999, 6, 6));
5562         }
5563
5564         {
5565             auto date = Date(1999, 5, 31);
5566             date.roll!"months"(1, AllowDayOverflow.no);
5567             assert(date == Date(1999, 6, 30));
5568         }
5569
5570         {
5571             auto date = Date(1999, 5, 31);
5572             date.roll!"months"(-1, AllowDayOverflow.no);
5573             assert(date == Date(1999, 4, 30));
5574         }
5575
5576         {
5577             auto date = Date(1999, 2, 28);
5578             date.roll!"months"(12, AllowDayOverflow.no);
5579             assert(date == Date(1999, 2, 28));
5580         }
5581
5582         {
5583             auto date = Date(2000, 2, 29);
5584             date.roll!"months"(12, AllowDayOverflow.no);
5585             assert(date == Date(2000, 2, 29));
5586         }
5587
5588         {
5589             auto date = Date(1999, 7, 31);
5590             date.roll!"months"(1, AllowDayOverflow.no);
5591             assert(date == Date(1999, 8, 31));
5592             date.roll!"months"(1, AllowDayOverflow.no);
5593             assert(date == Date(1999, 9, 30));
5594         }
5595
5596         {
5597             auto date = Date(1998, 8, 31);
5598             date.roll!"months"(13, AllowDayOverflow.no);
5599             assert(date == Date(1998, 9, 30));
5600             date.roll!"months"(-13, AllowDayOverflow.no);
5601             assert(date == Date(1998, 8, 30));
5602         }
5603
5604         {
5605             auto date = Date(1997, 12, 31);
5606             date.roll!"months"(13, AllowDayOverflow.no);
5607             assert(date == Date(1997, 1, 31));
5608             date.roll!"months"(-13, AllowDayOverflow.no);
5609             assert(date == Date(1997, 12, 31));
5610         }
5611
5612         {
5613             auto date = Date(1997, 12, 31);
5614             date.roll!"months"(14, AllowDayOverflow.no);
5615             assert(date == Date(1997, 2, 28));
5616             date.roll!"months"(-14, AllowDayOverflow.no);
5617             assert(date == Date(1997, 12, 28));
5618         }
5619
5620         {
5621             auto date = Date(1998, 12, 31);
5622             date.roll!"months"(14, AllowDayOverflow.no);
5623             assert(date == Date(1998, 2, 28));
5624             date.roll!"months"(-14, AllowDayOverflow.no);
5625             assert(date == Date(1998, 12, 28));
5626         }
5627
5628         {
5629             auto date = Date(1999, 12, 31);
5630             date.roll!"months"(14, AllowDayOverflow.no);
5631             assert(date == Date(1999, 2, 28));
5632             date.roll!"months"(-14, AllowDayOverflow.no);
5633             assert(date == Date(1999, 12, 28));
5634         }
5635
5636         // Test B.C.
5637         {
5638             auto date = Date(-1999, 7, 6);
5639             date.roll!"months"(3, AllowDayOverflow.no);
5640             assert(date == Date(-1999, 10, 6));
5641             date.roll!"months"(-4, AllowDayOverflow.no);
5642             assert(date == Date(-1999, 6, 6));
5643         }
5644
5645         {
5646             auto date = Date(-1999, 7, 6);
5647             date.roll!"months"(6, AllowDayOverflow.no);
5648             assert(date == Date(-1999, 1, 6));
5649             date.roll!"months"(-6, AllowDayOverflow.no);
5650             assert(date == Date(-1999, 7, 6));
5651         }
5652
5653         {
5654             auto date = Date(-1999, 7, 6);
5655             date.roll!"months"(-27, AllowDayOverflow.no);
5656             assert(date == Date(-1999, 4, 6));
5657             date.roll!"months"(28, AllowDayOverflow.no);
5658             assert(date == Date(-1999, 8, 6));
5659         }
5660
5661         {
5662             auto date = Date(-1999, 5, 31);
5663             date.roll!"months"(1, AllowDayOverflow.no);
5664             assert(date == Date(-1999, 6, 30));
5665         }
5666
5667         {
5668             auto date = Date(-1999, 5, 31);
5669             date.roll!"months"(-1, AllowDayOverflow.no);
5670             assert(date == Date(-1999, 4, 30));
5671         }
5672
5673         {
5674             auto date = Date(-1999, 2, 28);
5675             date.roll!"months"(-12, AllowDayOverflow.no);
5676             assert(date == Date(-1999, 2, 28));
5677         }
5678
5679         {
5680             auto date = Date(-2000, 2, 29);
5681             date.roll!"months"(-12, AllowDayOverflow.no);
5682             assert(date == Date(-2000, 2, 29));
5683         }
5684
5685         {
5686             auto date = Date(-1999, 7, 31);
5687             date.roll!"months"(1, AllowDayOverflow.no);
5688             assert(date == Date(-1999, 8, 31));
5689             date.roll!"months"(1, AllowDayOverflow.no);
5690             assert(date == Date(-1999, 9, 30));
5691         }
5692
5693         {
5694             auto date = Date(-1998, 8, 31);
5695             date.roll!"months"(13, AllowDayOverflow.no);
5696             assert(date == Date(-1998, 9, 30));
5697             date.roll!"months"(-13, AllowDayOverflow.no);
5698             assert(date == Date(-1998, 8, 30));
5699         }
5700
5701         {
5702             auto date = Date(-1997, 12, 31);
5703             date.roll!"months"(13, AllowDayOverflow.no);
5704             assert(date == Date(-1997, 1, 31));
5705             date.roll!"months"(-13, AllowDayOverflow.no);
5706             assert(date == Date(-1997, 12, 31));
5707         }
5708
5709         {
5710             auto date = Date(-1997, 12, 31);
5711             date.roll!"months"(14, AllowDayOverflow.no);
5712             assert(date == Date(-1997, 2, 28));
5713             date.roll!"months"(-14, AllowDayOverflow.no);
5714             assert(date == Date(-1997, 12, 28));
5715         }
5716
5717         {
5718             auto date = Date(-2002, 12, 31);
5719             date.roll!"months"(14, AllowDayOverflow.no);
5720             assert(date == Date(-2002, 2, 28));
5721             date.roll!"months"(-14, AllowDayOverflow.no);
5722             assert(date == Date(-2002, 12, 28));
5723         }
5724
5725         {
5726             auto date = Date(-2001, 12, 31);
5727             date.roll!"months"(14, AllowDayOverflow.no);
5728             assert(date == Date(-2001, 2, 28));
5729             date.roll!"months"(-14, AllowDayOverflow.no);
5730             assert(date == Date(-2001, 12, 28));
5731         }
5732
5733         // Test Both
5734         {
5735             auto date = Date(1, 1, 1);
5736             date.roll!"months"(-1, AllowDayOverflow.no);
5737             assert(date == Date(1, 12, 1));
5738             date.roll!"months"(1, AllowDayOverflow.no);
5739             assert(date == Date(1, 1, 1));
5740         }
5741
5742         {
5743             auto date = Date(4, 1, 1);
5744             date.roll!"months"(-48, AllowDayOverflow.no);
5745             assert(date == Date(4, 1, 1));
5746             date.roll!"months"(48, AllowDayOverflow.no);
5747             assert(date == Date(4, 1, 1));
5748         }
5749
5750         {
5751             auto date = Date(4, 3, 31);
5752             date.roll!"months"(-49, AllowDayOverflow.no);
5753             assert(date == Date(4, 2, 29));
5754             date.roll!"months"(49, AllowDayOverflow.no);
5755             assert(date == Date(4, 3, 29));
5756         }
5757
5758         {
5759             auto date = Date(4, 3, 31);
5760             date.roll!"months"(-85, AllowDayOverflow.no);
5761             assert(date == Date(4, 2, 29));
5762             date.roll!"months"(85, AllowDayOverflow.no);
5763             assert(date == Date(4, 3, 29));
5764         }
5765
5766         {
5767             auto date = Date(-1, 1, 1);
5768             date.roll!"months"(-1, AllowDayOverflow.no);
5769             assert(date == Date(-1, 12, 1));
5770             date.roll!"months"(1, AllowDayOverflow.no);
5771             assert(date == Date(-1, 1, 1));
5772         }
5773
5774         {
5775             auto date = Date(-4, 1, 1);
5776             date.roll!"months"(-48, AllowDayOverflow.no);
5777             assert(date == Date(-4, 1, 1));
5778             date.roll!"months"(48, AllowDayOverflow.no);
5779             assert(date == Date(-4, 1, 1));
5780         }
5781
5782         {
5783             auto date = Date(-4, 3, 31);
5784             date.roll!"months"(-49, AllowDayOverflow.no);
5785             assert(date == Date(-4, 2, 29));
5786             date.roll!"months"(49, AllowDayOverflow.no);
5787             assert(date == Date(-4, 3, 29));
5788         }
5789
5790         {
5791             auto date = Date(-4, 3, 31);
5792             date.roll!"months"(-85, AllowDayOverflow.no);
5793             assert(date == Date(-4, 2, 29));
5794             date.roll!"months"(85, AllowDayOverflow.no);
5795             assert(date == Date(-4, 3, 29));
5796         }
5797
5798         {
5799             auto date = Date(-3, 3, 31);
5800             date.roll!"months"(85, AllowDayOverflow.no).roll!"months"(-83, AllowDayOverflow.no);
5801             assert(date == Date(-3, 5, 30));
5802         }
5803     }
5804
5805
5806     /++
5807         Adds the given number of units to this $(LREF Date). A negative number
5808         will subtract.
5809
5810         The difference between rolling and adding is that rolling does not
5811         affect larger units. For instance, rolling a $(LREF Date) one
5812         year's worth of days gets the exact same $(LREF Date).
5813
5814         The only accepted units are $(D "days").
5815
5816         Params:
5817             units = The units to add. Must be $(D "days").
5818             days  = The number of days to add to this $(LREF Date).
5819       +/
5820     ref Date roll(string units)(long days) @safe pure nothrow @nogc
5821         if (units == "days")
5822     {
5823         immutable limit = maxDay(_year, _month);
5824         days %= limit;
5825         auto newDay = _day + days;
5826
5827         if (days < 0)
5828         {
5829             if (newDay < 1)
5830                 newDay += limit;
5831         }
5832         else if (newDay > limit)
5833             newDay -= limit;
5834
5835         _day = cast(ubyte) newDay;
5836         return this;
5837     }
5838
5839     ///
5840     @safe unittest
5841     {
5842         auto d = Date(2010, 1, 1);
5843         d.roll!"days"(1);
5844         assert(d == Date(2010, 1, 2));
5845         d.roll!"days"(365);
5846         assert(d == Date(2010, 1, 26));
5847         d.roll!"days"(-32);
5848         assert(d == Date(2010, 1, 25));
5849     }
5850
5851     @safe unittest
5852     {
5853         // Test A.D.
5854         {
5855             auto date = Date(1999, 2, 28);
5856             date.roll!"days"(1);
5857             assert(date == Date(1999, 2, 1));
5858             date.roll!"days"(-1);
5859             assert(date == Date(1999, 2, 28));
5860         }
5861
5862         {
5863             auto date = Date(2000, 2, 28);
5864             date.roll!"days"(1);
5865             assert(date == Date(2000, 2, 29));
5866             date.roll!"days"(1);
5867             assert(date == Date(2000, 2, 1));
5868             date.roll!"days"(-1);
5869             assert(date == Date(2000, 2, 29));
5870         }
5871
5872         {
5873             auto date = Date(1999, 6, 30);
5874             date.roll!"days"(1);
5875             assert(date == Date(1999, 6, 1));
5876             date.roll!"days"(-1);
5877             assert(date == Date(1999, 6, 30));
5878         }
5879
5880         {
5881             auto date = Date(1999, 7, 31);
5882             date.roll!"days"(1);
5883             assert(date == Date(1999, 7, 1));
5884             date.roll!"days"(-1);
5885             assert(date == Date(1999, 7, 31));
5886         }
5887
5888         {
5889             auto date = Date(1999, 1, 1);
5890             date.roll!"days"(-1);
5891             assert(date == Date(1999, 1, 31));
5892             date.roll!"days"(1);
5893             assert(date == Date(1999, 1, 1));
5894         }
5895
5896         {
5897             auto date = Date(1999, 7, 6);
5898             date.roll!"days"(9);
5899             assert(date == Date(1999, 7, 15));
5900             date.roll!"days"(-11);
5901             assert(date == Date(1999, 7, 4));
5902             date.roll!"days"(30);
5903             assert(date == Date(1999, 7, 3));
5904             date.roll!"days"(-3);
5905             assert(date == Date(1999, 7, 31));
5906         }
5907
5908         {
5909             auto date = Date(1999, 7, 6);
5910             date.roll!"days"(365);
5911             assert(date == Date(1999, 7, 30));
5912             date.roll!"days"(-365);
5913             assert(date == Date(1999, 7, 6));
5914             date.roll!"days"(366);
5915             assert(date == Date(1999, 7, 31));
5916             date.roll!"days"(730);
5917             assert(date == Date(1999, 7, 17));
5918             date.roll!"days"(-1096);
5919             assert(date == Date(1999, 7, 6));
5920         }
5921
5922         {
5923             auto date = Date(1999, 2, 6);
5924             date.roll!"days"(365);
5925             assert(date == Date(1999, 2, 7));
5926             date.roll!"days"(-365);
5927             assert(date == Date(1999, 2, 6));
5928             date.roll!"days"(366);
5929             assert(date == Date(1999, 2, 8));
5930             date.roll!"days"(730);
5931             assert(date == Date(1999, 2, 10));
5932             date.roll!"days"(-1096);
5933             assert(date == Date(1999, 2, 6));
5934         }
5935
5936         // Test B.C.
5937         {
5938             auto date = Date(-1999, 2, 28);
5939             date.roll!"days"(1);
5940             assert(date == Date(-1999, 2, 1));
5941             date.roll!"days"(-1);
5942             assert(date == Date(-1999, 2, 28));
5943         }
5944
5945         {
5946             auto date = Date(-2000, 2, 28);
5947             date.roll!"days"(1);
5948             assert(date == Date(-2000, 2, 29));
5949             date.roll!"days"(1);
5950             assert(date == Date(-2000, 2, 1));
5951             date.roll!"days"(-1);
5952             assert(date == Date(-2000, 2, 29));
5953         }
5954
5955         {
5956             auto date = Date(-1999, 6, 30);
5957             date.roll!"days"(1);
5958             assert(date == Date(-1999, 6, 1));
5959             date.roll!"days"(-1);
5960             assert(date == Date(-1999, 6, 30));
5961         }
5962
5963         {
5964             auto date = Date(-1999, 7, 31);
5965             date.roll!"days"(1);
5966             assert(date == Date(-1999, 7, 1));
5967             date.roll!"days"(-1);
5968             assert(date == Date(-1999, 7, 31));
5969         }
5970
5971         {
5972             auto date = Date(-1999, 1, 1);
5973             date.roll!"days"(-1);
5974             assert(date == Date(-1999, 1, 31));
5975             date.roll!"days"(1);
5976             assert(date == Date(-1999, 1, 1));
5977         }
5978
5979         {
5980             auto date = Date(-1999, 7, 6);
5981             date.roll!"days"(9);
5982             assert(date == Date(-1999, 7, 15));
5983             date.roll!"days"(-11);
5984             assert(date == Date(-1999, 7, 4));
5985             date.roll!"days"(30);
5986             assert(date == Date(-1999, 7, 3));
5987             date.roll!"days"(-3);
5988             assert(date == Date(-1999, 7, 31));
5989         }
5990
5991         {
5992             auto date = Date(-1999, 7, 6);
5993             date.roll!"days"(365);
5994             assert(date == Date(-1999, 7, 30));
5995             date.roll!"days"(-365);
5996             assert(date == Date(-1999, 7, 6));
5997             date.roll!"days"(366);
5998             assert(date == Date(-1999, 7, 31));
5999             date.roll!"days"(730);
6000             assert(date == Date(-1999, 7, 17));
6001             date.roll!"days"(-1096);
6002             assert(date == Date(-1999, 7, 6));
6003         }
6004
6005         // Test Both
6006         {
6007             auto date = Date(1, 7, 6);
6008             date.roll!"days"(-365);
6009             assert(date == Date(1, 7, 13));
6010             date.roll!"days"(365);
6011             assert(date == Date(1, 7, 6));
6012             date.roll!"days"(-731);
6013             assert(date == Date(1, 7, 19));
6014             date.roll!"days"(730);
6015             assert(date == Date(1, 7, 5));
6016         }
6017
6018         {
6019             auto date = Date(0, 7, 6);
6020             date.roll!"days"(-365);
6021             assert(date == Date(0, 7, 13));
6022             date.roll!"days"(365);
6023             assert(date == Date(0, 7, 6));
6024             date.roll!"days"(-731);
6025             assert(date == Date(0, 7, 19));
6026             date.roll!"days"(730);
6027             assert(date == Date(0, 7, 5));
6028         }
6029
6030         {
6031             auto date = Date(0, 7, 6);
6032             date.roll!"days"(-365).roll!"days"(362).roll!"days"(-12).roll!"days"(730);
6033             assert(date == Date(0, 7, 8));
6034         }
6035
6036         const cdate = Date(1999, 7, 6);
6037         immutable idate = Date(1999, 7, 6);
6038         static assert(!__traits(compiles, cdate.roll!"days"(12)));
6039         static assert(!__traits(compiles, idate.roll!"days"(12)));
6040     }
6041
6042
6043     /++
6044         Gives the result of adding or subtracting a $(REF Duration, core,time)
6045         from
6046
6047         The legal types of arithmetic for $(LREF Date) using this operator are
6048
6049         $(BOOKTABLE,
6050         $(TR $(TD Date) $(TD +) $(TD Duration) $(TD -->) $(TD Date))
6051         $(TR $(TD Date) $(TD -) $(TD Duration) $(TD -->) $(TD Date))
6052         )
6053
6054         Params:
6055             duration = The $(REF Duration, core,time) to add to or subtract from
6056                        this $(LREF Date).
6057       +/
6058     Date opBinary(string op)(Duration duration) const @safe pure nothrow @nogc
6059         if (op == "+" || op == "-")
6060     {
6061         Date retval = this;
6062         immutable days = duration.total!"days";
6063         mixin("return retval._addDays(" ~ op ~ "days);");
6064     }
6065
6066     ///
6067     @safe unittest
6068     {
6069         import core.time : days;
6070
6071         assert(Date(2015, 12, 31) + days(1) == Date(2016, 1, 1));
6072         assert(Date(2004, 2, 26) + days(4) == Date(2004, 3, 1));
6073
6074         assert(Date(2016, 1, 1) - days(1) == Date(2015, 12, 31));
6075         assert(Date(2004, 3, 1) - days(4) == Date(2004, 2, 26));
6076     }
6077
6078     @safe unittest
6079     {
6080         auto date = Date(1999, 7, 6);
6081
6082         assert(date + dur!"weeks"(7) == Date(1999, 8, 24));
6083         assert(date + dur!"weeks"(-7) == Date(1999, 5, 18));
6084         assert(date + dur!"days"(7) == Date(1999, 7, 13));
6085         assert(date + dur!"days"(-7) == Date(1999, 6, 29));
6086
6087         assert(date + dur!"hours"(24) == Date(1999, 7, 7));
6088         assert(date + dur!"hours"(-24) == Date(1999, 7, 5));
6089         assert(date + dur!"minutes"(1440) == Date(1999, 7, 7));
6090         assert(date + dur!"minutes"(-1440) == Date(1999, 7, 5));
6091         assert(date + dur!"seconds"(86_400) == Date(1999, 7, 7));
6092         assert(date + dur!"seconds"(-86_400) == Date(1999, 7, 5));
6093         assert(date + dur!"msecs"(86_400_000) == Date(1999, 7, 7));
6094         assert(date + dur!"msecs"(-86_400_000) == Date(1999, 7, 5));
6095         assert(date + dur!"usecs"(86_400_000_000) == Date(1999, 7, 7));
6096         assert(date + dur!"usecs"(-86_400_000_000) == Date(1999, 7, 5));
6097         assert(date + dur!"hnsecs"(864_000_000_000) == Date(1999, 7, 7));
6098         assert(date + dur!"hnsecs"(-864_000_000_000) == Date(1999, 7, 5));
6099
6100         assert(date - dur!"weeks"(-7) == Date(1999, 8, 24));
6101         assert(date - dur!"weeks"(7) == Date(1999, 5, 18));
6102         assert(date - dur!"days"(-7) == Date(1999, 7, 13));
6103         assert(date - dur!"days"(7) == Date(1999, 6, 29));
6104
6105         assert(date - dur!"hours"(-24) == Date(1999, 7, 7));
6106         assert(date - dur!"hours"(24) == Date(1999, 7, 5));
6107         assert(date - dur!"minutes"(-1440) == Date(1999, 7, 7));
6108         assert(date - dur!"minutes"(1440) == Date(1999, 7, 5));
6109         assert(date - dur!"seconds"(-86_400) == Date(1999, 7, 7));
6110         assert(date - dur!"seconds"(86_400) == Date(1999, 7, 5));
6111         assert(date - dur!"msecs"(-86_400_000) == Date(1999, 7, 7));
6112         assert(date - dur!"msecs"(86_400_000) == Date(1999, 7, 5));
6113         assert(date - dur!"usecs"(-86_400_000_000) == Date(1999, 7, 7));
6114         assert(date - dur!"usecs"(86_400_000_000) == Date(1999, 7, 5));
6115         assert(date - dur!"hnsecs"(-864_000_000_000) == Date(1999, 7, 7));
6116         assert(date - dur!"hnsecs"(864_000_000_000) == Date(1999, 7, 5));
6117
6118         auto duration = dur!"days"(12);
6119         const cdate = Date(1999, 7, 6);
6120         immutable idate = Date(1999, 7, 6);
6121         assert(date + duration == Date(1999, 7, 18));
6122         assert(cdate + duration == Date(1999, 7, 18));
6123         assert(idate + duration == Date(1999, 7, 18));
6124
6125         assert(date - duration == Date(1999, 6, 24));
6126         assert(cdate - duration == Date(1999, 6, 24));
6127         assert(idate - duration == Date(1999, 6, 24));
6128     }
6129
6130     // Explicitly undocumented. It will be removed in January 2018. @@@DEPRECATED_2018-01@@@
6131     deprecated("Use Duration instead of TickDuration.")
6132     Date opBinary(string op)(TickDuration td) const @safe pure nothrow @nogc
6133         if (op == "+" || op == "-")
6134     {
6135         Date retval = this;
6136         immutable days = convert!("hnsecs", "days")(td.hnsecs);
6137         mixin("return retval._addDays(" ~ op ~ "days);");
6138     }
6139
6140     deprecated @safe unittest
6141     {
6142         // This probably only runs in cases where gettimeofday() is used, but it's
6143         // hard to do this test correctly with variable ticksPerSec.
6144         if (TickDuration.ticksPerSec == 1_000_000)
6145         {
6146             auto date = Date(1999, 7, 6);
6147
6148             assert(date + TickDuration.from!"usecs"(86_400_000_000) == Date(1999, 7, 7));
6149             assert(date + TickDuration.from!"usecs"(-86_400_000_000) == Date(1999, 7, 5));
6150
6151             assert(date - TickDuration.from!"usecs"(-86_400_000_000) == Date(1999, 7, 7));
6152             assert(date - TickDuration.from!"usecs"(86_400_000_000) == Date(1999, 7, 5));
6153         }
6154     }
6155
6156
6157     /++
6158         Gives the result of adding or subtracting a $(REF Duration, core,time)
6159         from this $(LREF Date), as well as assigning the result to this
6160         $(LREF Date).
6161
6162         The legal types of arithmetic for $(LREF Date) using this operator are
6163
6164         $(BOOKTABLE,
6165         $(TR $(TD Date) $(TD +) $(TD Duration) $(TD -->) $(TD Date))
6166         $(TR $(TD Date) $(TD -) $(TD Duration) $(TD -->) $(TD Date))
6167         )
6168
6169         Params:
6170             duration = The $(REF Duration, core,time) to add to or subtract from
6171                        this $(LREF Date).
6172       +/
6173     ref Date opOpAssign(string op)(Duration duration) @safe pure nothrow @nogc
6174         if (op == "+" || op == "-")
6175     {
6176         immutable days = duration.total!"days";
6177         mixin("return _addDays(" ~ op ~ "days);");
6178     }
6179
6180     @safe unittest
6181     {
6182         assert(Date(1999, 7, 6) + dur!"weeks"(7) == Date(1999, 8, 24));
6183         assert(Date(1999, 7, 6) + dur!"weeks"(-7) == Date(1999, 5, 18));
6184         assert(Date(1999, 7, 6) + dur!"days"(7) == Date(1999, 7, 13));
6185         assert(Date(1999, 7, 6) + dur!"days"(-7) == Date(1999, 6, 29));
6186
6187         assert(Date(1999, 7, 6) + dur!"hours"(24) == Date(1999, 7, 7));
6188         assert(Date(1999, 7, 6) + dur!"hours"(-24) == Date(1999, 7, 5));
6189         assert(Date(1999, 7, 6) + dur!"minutes"(1440) == Date(1999, 7, 7));
6190         assert(Date(1999, 7, 6) + dur!"minutes"(-1440) == Date(1999, 7, 5));
6191         assert(Date(1999, 7, 6) + dur!"seconds"(86_400) == Date(1999, 7, 7));
6192         assert(Date(1999, 7, 6) + dur!"seconds"(-86_400) == Date(1999, 7, 5));
6193         assert(Date(1999, 7, 6) + dur!"msecs"(86_400_000) == Date(1999, 7, 7));
6194         assert(Date(1999, 7, 6) + dur!"msecs"(-86_400_000) == Date(1999, 7, 5));
6195         assert(Date(1999, 7, 6) + dur!"usecs"(86_400_000_000) == Date(1999, 7, 7));
6196         assert(Date(1999, 7, 6) + dur!"usecs"(-86_400_000_000) == Date(1999, 7, 5));
6197         assert(Date(1999, 7, 6) + dur!"hnsecs"(864_000_000_000) == Date(1999, 7, 7));
6198         assert(Date(1999, 7, 6) + dur!"hnsecs"(-864_000_000_000) == Date(1999, 7, 5));
6199
6200         assert(Date(1999, 7, 6) - dur!"weeks"(-7) == Date(1999, 8, 24));
6201         assert(Date(1999, 7, 6) - dur!"weeks"(7) == Date(1999, 5, 18));
6202         assert(Date(1999, 7, 6) - dur!"days"(-7) == Date(1999, 7, 13));
6203         assert(Date(1999, 7, 6) - dur!"days"(7) == Date(1999, 6, 29));
6204
6205         assert(Date(1999, 7, 6) - dur!"hours"(-24) == Date(1999, 7, 7));
6206         assert(Date(1999, 7, 6) - dur!"hours"(24) == Date(1999, 7, 5));
6207         assert(Date(1999, 7, 6) - dur!"minutes"(-1440) == Date(1999, 7, 7));
6208         assert(Date(1999, 7, 6) - dur!"minutes"(1440) == Date(1999, 7, 5));
6209         assert(Date(1999, 7, 6) - dur!"seconds"(-86_400) == Date(1999, 7, 7));
6210         assert(Date(1999, 7, 6) - dur!"seconds"(86_400) == Date(1999, 7, 5));
6211         assert(Date(1999, 7, 6) - dur!"msecs"(-86_400_000) == Date(1999, 7, 7));
6212         assert(Date(1999, 7, 6) - dur!"msecs"(86_400_000) == Date(1999, 7, 5));
6213         assert(Date(1999, 7, 6) - dur!"usecs"(-86_400_000_000) == Date(1999, 7, 7));
6214         assert(Date(1999, 7, 6) - dur!"usecs"(86_400_000_000) == Date(1999, 7, 5));
6215         assert(Date(1999, 7, 6) - dur!"hnsecs"(-864_000_000_000) == Date(1999, 7, 7));
6216         assert(Date(1999, 7, 6) - dur!"hnsecs"(864_000_000_000) == Date(1999, 7, 5));
6217
6218         {
6219             auto date = Date(0, 1, 31);
6220             (date += dur!"days"(507)) += dur!"days"(-2);
6221             assert(date == Date(1, 6, 19));
6222         }
6223
6224         auto duration = dur!"days"(12);
6225         auto date = Date(1999, 7, 6);
6226         const cdate = Date(1999, 7, 6);
6227         immutable idate = Date(1999, 7, 6);
6228         date += duration;
6229         static assert(!__traits(compiles, cdate += duration));
6230         static assert(!__traits(compiles, idate += duration));
6231
6232         date -= duration;
6233         static assert(!__traits(compiles, cdate -= duration));
6234         static assert(!__traits(compiles, idate -= duration));
6235     }
6236
6237     // Explicitly undocumented. It will be removed in January 2018. @@@DEPRECATED_2018-01@@@
6238     deprecated("Use Duration instead of TickDuration.")
6239     ref Date opOpAssign(string op)(TickDuration td) @safe pure nothrow @nogc
6240         if (op == "+" || op == "-")
6241     {
6242         immutable days = convert!("seconds", "days")(td.seconds);
6243         mixin("return _addDays(" ~ op ~ "days);");
6244     }
6245
6246     deprecated @safe unittest
6247     {
6248         // This probably only runs in cases where gettimeofday() is used, but it's
6249         // hard to do this test correctly with variable ticksPerSec.
6250         if (TickDuration.ticksPerSec == 1_000_000)
6251         {
6252             {
6253                 auto date = Date(1999, 7, 6);
6254                 date += TickDuration.from!"usecs"(86_400_000_000);
6255                 assert(date == Date(1999, 7, 7));
6256             }
6257
6258             {
6259                 auto date = Date(1999, 7, 6);
6260                 date += TickDuration.from!"usecs"(-86_400_000_000);
6261                 assert(date == Date(1999, 7, 5));
6262             }
6263
6264             {
6265                 auto date = Date(1999, 7, 6);
6266                 date -= TickDuration.from!"usecs"(-86_400_000_000);
6267                 assert(date == Date(1999, 7, 7));
6268             }
6269
6270             {
6271                 auto date = Date(1999, 7, 6);
6272                 date -= TickDuration.from!"usecs"(86_400_000_000);
6273                 assert(date == Date(1999, 7, 5));
6274             }
6275         }
6276     }
6277
6278
6279     /++
6280         Gives the difference between two $(LREF Date)s.
6281
6282         The legal types of arithmetic for $(LREF Date) using this operator are
6283
6284         $(BOOKTABLE,
6285         $(TR $(TD Date) $(TD -) $(TD Date) $(TD -->) $(TD duration))
6286         )
6287       +/
6288     Duration opBinary(string op)(in Date rhs) const @safe pure nothrow @nogc
6289         if (op == "-")
6290     {
6291         return dur!"days"(this.dayOfGregorianCal - rhs.dayOfGregorianCal);
6292     }
6293
6294     @safe unittest
6295     {
6296         auto date = Date(1999, 7, 6);
6297
6298         assert(Date(1999, 7, 6) - Date(1998, 7, 6) == dur!"days"(365));
6299         assert(Date(1998, 7, 6) - Date(1999, 7, 6) == dur!"days"(-365));
6300         assert(Date(1999, 6, 6) - Date(1999, 5, 6) == dur!"days"(31));
6301         assert(Date(1999, 5, 6) - Date(1999, 6, 6) == dur!"days"(-31));
6302         assert(Date(1999, 1, 1) - Date(1998, 12, 31) == dur!"days"(1));
6303         assert(Date(1998, 12, 31) - Date(1999, 1, 1) == dur!"days"(-1));
6304
6305         const cdate = Date(1999, 7, 6);
6306         immutable idate = Date(1999, 7, 6);
6307         assert(date - date == Duration.zero);
6308         assert(cdate - date == Duration.zero);
6309         assert(idate - date == Duration.zero);
6310
6311         assert(date - cdate == Duration.zero);
6312         assert(cdate - cdate == Duration.zero);
6313         assert(idate - cdate == Duration.zero);
6314
6315         assert(date - idate == Duration.zero);
6316         assert(cdate - idate == Duration.zero);
6317         assert(idate - idate == Duration.zero);
6318     }
6319
6320
6321     /++
6322         Returns the difference between the two $(LREF Date)s in months.
6323
6324         To get the difference in years, subtract the year property
6325         of two $(LREF Date)s. To get the difference in days or weeks,
6326         subtract the $(LREF Date)s themselves and use the
6327         $(REF Duration, core,time) that results. Because converting between
6328         months and smaller units requires a specific date (which
6329         $(REF Duration, core,time)s don't have), getting the difference in
6330         months requires some math using both the year and month properties, so
6331         this is a convenience function for getting the difference in months.
6332
6333         Note that the number of days in the months or how far into the month
6334         either $(LREF Date) is is irrelevant. It is the difference in the month
6335         property combined with the difference in years * 12. So, for instance,
6336         December 31st and January 1st are one month apart just as December 1st
6337         and January 31st are one month apart.
6338
6339         Params:
6340             rhs = The $(LREF Date) to subtract from this one.
6341       +/
6342     int diffMonths(in Date rhs) const @safe pure nothrow @nogc
6343     {
6344         immutable yearDiff = _year - rhs._year;
6345         immutable monthDiff = _month - rhs._month;
6346
6347         return yearDiff * 12 + monthDiff;
6348     }
6349
6350     ///
6351     @safe unittest
6352     {
6353         assert(Date(1999, 2, 1).diffMonths(Date(1999, 1, 31)) == 1);
6354         assert(Date(1999, 1, 31).diffMonths(Date(1999, 2, 1)) == -1);
6355         assert(Date(1999, 3, 1).diffMonths(Date(1999, 1, 1)) == 2);
6356         assert(Date(1999, 1, 1).diffMonths(Date(1999, 3, 31)) == -2);
6357     }
6358
6359     @safe unittest
6360     {
6361         auto date = Date(1999, 7, 6);
6362
6363         // Test A.D.
6364         assert(date.diffMonths(Date(1998, 6, 5)) == 13);
6365         assert(date.diffMonths(Date(1998, 7, 5)) == 12);
6366         assert(date.diffMonths(Date(1998, 8, 5)) == 11);
6367         assert(date.diffMonths(Date(1998, 9, 5)) == 10);
6368         assert(date.diffMonths(Date(1998, 10, 5)) == 9);
6369         assert(date.diffMonths(Date(1998, 11, 5)) == 8);
6370         assert(date.diffMonths(Date(1998, 12, 5)) == 7);
6371         assert(date.diffMonths(Date(1999, 1, 5)) == 6);
6372         assert(date.diffMonths(Date(1999, 2, 6)) == 5);
6373         assert(date.diffMonths(Date(1999, 3, 6)) == 4);
6374         assert(date.diffMonths(Date(1999, 4, 6)) == 3);
6375         assert(date.diffMonths(Date(1999, 5, 6)) == 2);
6376         assert(date.diffMonths(Date(1999, 6, 6)) == 1);
6377         assert(date.diffMonths(date) == 0);
6378         assert(date.diffMonths(Date(1999, 8, 6)) == -1);
6379         assert(date.diffMonths(Date(1999, 9, 6)) == -2);
6380         assert(date.diffMonths(Date(1999, 10, 6)) == -3);
6381         assert(date.diffMonths(Date(1999, 11, 6)) == -4);
6382         assert(date.diffMonths(Date(1999, 12, 6)) == -5);
6383         assert(date.diffMonths(Date(2000, 1, 6)) == -6);
6384         assert(date.diffMonths(Date(2000, 2, 6)) == -7);
6385         assert(date.diffMonths(Date(2000, 3, 6)) == -8);
6386         assert(date.diffMonths(Date(2000, 4, 6)) == -9);
6387         assert(date.diffMonths(Date(2000, 5, 6)) == -10);
6388         assert(date.diffMonths(Date(2000, 6, 6)) == -11);
6389         assert(date.diffMonths(Date(2000, 7, 6)) == -12);
6390         assert(date.diffMonths(Date(2000, 8, 6)) == -13);
6391
6392         assert(Date(1998, 6, 5).diffMonths(date) == -13);
6393         assert(Date(1998, 7, 5).diffMonths(date) == -12);
6394         assert(Date(1998, 8, 5).diffMonths(date) == -11);
6395         assert(Date(1998, 9, 5).diffMonths(date) == -10);
6396         assert(Date(1998, 10, 5).diffMonths(date) == -9);
6397         assert(Date(1998, 11, 5).diffMonths(date) == -8);
6398         assert(Date(1998, 12, 5).diffMonths(date) == -7);
6399         assert(Date(1999, 1, 5).diffMonths(date) == -6);
6400         assert(Date(1999, 2, 6).diffMonths(date) == -5);
6401         assert(Date(1999, 3, 6).diffMonths(date) == -4);
6402         assert(Date(1999, 4, 6).diffMonths(date) == -3);
6403         assert(Date(1999, 5, 6).diffMonths(date) == -2);
6404         assert(Date(1999, 6, 6).diffMonths(date) == -1);
6405         assert(Date(1999, 8, 6).diffMonths(date) == 1);
6406         assert(Date(1999, 9, 6).diffMonths(date) == 2);
6407         assert(Date(1999, 10, 6).diffMonths(date) == 3);
6408         assert(Date(1999, 11, 6).diffMonths(date) == 4);
6409         assert(Date(1999, 12, 6).diffMonths(date) == 5);
6410         assert(Date(2000, 1, 6).diffMonths(date) == 6);
6411         assert(Date(2000, 2, 6).diffMonths(date) == 7);
6412         assert(Date(2000, 3, 6).diffMonths(date) == 8);
6413         assert(Date(2000, 4, 6).diffMonths(date) == 9);
6414         assert(Date(2000, 5, 6).diffMonths(date) == 10);
6415         assert(Date(2000, 6, 6).diffMonths(date) == 11);
6416         assert(Date(2000, 7, 6).diffMonths(date) == 12);
6417         assert(Date(2000, 8, 6).diffMonths(date) == 13);
6418
6419         assert(date.diffMonths(Date(1999, 6, 30)) == 1);
6420         assert(date.diffMonths(Date(1999, 7, 1)) == 0);
6421         assert(date.diffMonths(Date(1999, 7, 6)) == 0);
6422         assert(date.diffMonths(Date(1999, 7, 11)) == 0);
6423         assert(date.diffMonths(Date(1999, 7, 16)) == 0);
6424         assert(date.diffMonths(Date(1999, 7, 21)) == 0);
6425         assert(date.diffMonths(Date(1999, 7, 26)) == 0);
6426         assert(date.diffMonths(Date(1999, 7, 31)) == 0);
6427         assert(date.diffMonths(Date(1999, 8, 1)) == -1);
6428
6429         assert(date.diffMonths(Date(1990, 6, 30)) == 109);
6430         assert(date.diffMonths(Date(1990, 7, 1)) == 108);
6431         assert(date.diffMonths(Date(1990, 7, 6)) == 108);
6432         assert(date.diffMonths(Date(1990, 7, 11)) == 108);
6433         assert(date.diffMonths(Date(1990, 7, 16)) == 108);
6434         assert(date.diffMonths(Date(1990, 7, 21)) == 108);
6435         assert(date.diffMonths(Date(1990, 7, 26)) == 108);
6436         assert(date.diffMonths(Date(1990, 7, 31)) == 108);
6437         assert(date.diffMonths(Date(1990, 8, 1)) == 107);
6438
6439         assert(Date(1999, 6, 30).diffMonths(date) == -1);
6440         assert(Date(1999, 7, 1).diffMonths(date) == 0);
6441         assert(Date(1999, 7, 6).diffMonths(date) == 0);
6442         assert(Date(1999, 7, 11).diffMonths(date) == 0);
6443         assert(Date(1999, 7, 16).diffMonths(date) == 0);
6444         assert(Date(1999, 7, 21).diffMonths(date) == 0);
6445         assert(Date(1999, 7, 26).diffMonths(date) == 0);
6446         assert(Date(1999, 7, 31).diffMonths(date) == 0);
6447         assert(Date(1999, 8, 1).diffMonths(date) == 1);
6448
6449         assert(Date(1990, 6, 30).diffMonths(date) == -109);
6450         assert(Date(1990, 7, 1).diffMonths(date) == -108);
6451         assert(Date(1990, 7, 6).diffMonths(date) == -108);
6452         assert(Date(1990, 7, 11).diffMonths(date) == -108);
6453         assert(Date(1990, 7, 16).diffMonths(date) == -108);
6454         assert(Date(1990, 7, 21).diffMonths(date) == -108);
6455         assert(Date(1990, 7, 26).diffMonths(date) == -108);
6456         assert(Date(1990, 7, 31).diffMonths(date) == -108);
6457         assert(Date(1990, 8, 1).diffMonths(date) == -107);
6458
6459         // Test B.C.
6460         auto dateBC = Date(-1999, 7, 6);
6461
6462         assert(dateBC.diffMonths(Date(-2000, 6, 5)) == 13);
6463         assert(dateBC.diffMonths(Date(-2000, 7, 5)) == 12);
6464         assert(dateBC.diffMonths(Date(-2000, 8, 5)) == 11);
6465         assert(dateBC.diffMonths(Date(-2000, 9, 5)) == 10);
6466         assert(dateBC.diffMonths(Date(-2000, 10, 5)) == 9);
6467         assert(dateBC.diffMonths(Date(-2000, 11, 5)) == 8);
6468         assert(dateBC.diffMonths(Date(-2000, 12, 5)) == 7);
6469         assert(dateBC.diffMonths(Date(-1999, 1, 5)) == 6);
6470         assert(dateBC.diffMonths(Date(-1999, 2, 6)) == 5);
6471         assert(dateBC.diffMonths(Date(-1999, 3, 6)) == 4);
6472         assert(dateBC.diffMonths(Date(-1999, 4, 6)) == 3);
6473         assert(dateBC.diffMonths(Date(-1999, 5, 6)) == 2);
6474         assert(dateBC.diffMonths(Date(-1999, 6, 6)) == 1);
6475         assert(dateBC.diffMonths(dateBC) == 0);
6476         assert(dateBC.diffMonths(Date(-1999, 8, 6)) == -1);
6477         assert(dateBC.diffMonths(Date(-1999, 9, 6)) == -2);
6478         assert(dateBC.diffMonths(Date(-1999, 10, 6)) == -3);
6479         assert(dateBC.diffMonths(Date(-1999, 11, 6)) == -4);
6480         assert(dateBC.diffMonths(Date(-1999, 12, 6)) == -5);
6481         assert(dateBC.diffMonths(Date(-1998, 1, 6)) == -6);
6482         assert(dateBC.diffMonths(Date(-1998, 2, 6)) == -7);
6483         assert(dateBC.diffMonths(Date(-1998, 3, 6)) == -8);
6484         assert(dateBC.diffMonths(Date(-1998, 4, 6)) == -9);
6485         assert(dateBC.diffMonths(Date(-1998, 5, 6)) == -10);
6486         assert(dateBC.diffMonths(Date(-1998, 6, 6)) == -11);
6487         assert(dateBC.diffMonths(Date(-1998, 7, 6)) == -12);
6488         assert(dateBC.diffMonths(Date(-1998, 8, 6)) == -13);
6489
6490         assert(Date(-2000, 6, 5).diffMonths(dateBC) == -13);
6491         assert(Date(-2000, 7, 5).diffMonths(dateBC) == -12);
6492         assert(Date(-2000, 8, 5).diffMonths(dateBC) == -11);
6493         assert(Date(-2000, 9, 5).diffMonths(dateBC) == -10);
6494         assert(Date(-2000, 10, 5).diffMonths(dateBC) == -9);
6495         assert(Date(-2000, 11, 5).diffMonths(dateBC) == -8);
6496         assert(Date(-2000, 12, 5).diffMonths(dateBC) == -7);
6497         assert(Date(-1999, 1, 5).diffMonths(dateBC) == -6);
6498         assert(Date(-1999, 2, 6).diffMonths(dateBC) == -5);
6499         assert(Date(-1999, 3, 6).diffMonths(dateBC) == -4);
6500         assert(Date(-1999, 4, 6).diffMonths(dateBC) == -3);
6501         assert(Date(-1999, 5, 6).diffMonths(dateBC) == -2);
6502         assert(Date(-1999, 6, 6).diffMonths(dateBC) == -1);
6503         assert(Date(-1999, 8, 6).diffMonths(dateBC) == 1);
6504         assert(Date(-1999, 9, 6).diffMonths(dateBC) == 2);
6505         assert(Date(-1999, 10, 6).diffMonths(dateBC) == 3);
6506         assert(Date(-1999, 11, 6).diffMonths(dateBC) == 4);
6507         assert(Date(-1999, 12, 6).diffMonths(dateBC) == 5);
6508         assert(Date(-1998, 1, 6).diffMonths(dateBC) == 6);
6509         assert(Date(-1998, 2, 6).diffMonths(dateBC) == 7);
6510         assert(Date(-1998, 3, 6).diffMonths(dateBC) == 8);
6511         assert(Date(-1998, 4, 6).diffMonths(dateBC) == 9);
6512         assert(Date(-1998, 5, 6).diffMonths(dateBC) == 10);
6513         assert(Date(-1998, 6, 6).diffMonths(dateBC) == 11);
6514         assert(Date(-1998, 7, 6).diffMonths(dateBC) == 12);
6515         assert(Date(-1998, 8, 6).diffMonths(dateBC) == 13);
6516
6517         assert(dateBC.diffMonths(Date(-1999, 6, 30)) == 1);
6518         assert(dateBC.diffMonths(Date(-1999, 7, 1)) == 0);
6519         assert(dateBC.diffMonths(Date(-1999, 7, 6)) == 0);
6520         assert(dateBC.diffMonths(Date(-1999, 7, 11)) == 0);
6521         assert(dateBC.diffMonths(Date(-1999, 7, 16)) == 0);
6522         assert(dateBC.diffMonths(Date(-1999, 7, 21)) == 0);
6523         assert(dateBC.diffMonths(Date(-1999, 7, 26)) == 0);
6524         assert(dateBC.diffMonths(Date(-1999, 7, 31)) == 0);
6525         assert(dateBC.diffMonths(Date(-1999, 8, 1)) == -1);
6526
6527         assert(dateBC.diffMonths(Date(-2008, 6, 30)) == 109);
6528         assert(dateBC.diffMonths(Date(-2008, 7, 1)) == 108);
6529         assert(dateBC.diffMonths(Date(-2008, 7, 6)) == 108);
6530         assert(dateBC.diffMonths(Date(-2008, 7, 11)) == 108);
6531         assert(dateBC.diffMonths(Date(-2008, 7, 16)) == 108);
6532         assert(dateBC.diffMonths(Date(-2008, 7, 21)) == 108);
6533         assert(dateBC.diffMonths(Date(-2008, 7, 26)) == 108);
6534         assert(dateBC.diffMonths(Date(-2008, 7, 31)) == 108);
6535         assert(dateBC.diffMonths(Date(-2008, 8, 1)) == 107);
6536
6537         assert(Date(-1999, 6, 30).diffMonths(dateBC) == -1);
6538         assert(Date(-1999, 7, 1).diffMonths(dateBC) == 0);
6539         assert(Date(-1999, 7, 6).diffMonths(dateBC) == 0);
6540         assert(Date(-1999, 7, 11).diffMonths(dateBC) == 0);
6541         assert(Date(-1999, 7, 16).diffMonths(dateBC) == 0);
6542         assert(Date(-1999, 7, 21).diffMonths(dateBC) == 0);
6543         assert(Date(-1999, 7, 26).diffMonths(dateBC) == 0);
6544         assert(Date(-1999, 7, 31).diffMonths(dateBC) == 0);
6545         assert(Date(-1999, 8, 1).diffMonths(dateBC) == 1);
6546
6547         assert(Date(-2008, 6, 30).diffMonths(dateBC) == -109);
6548         assert(Date(-2008, 7, 1).diffMonths(dateBC) == -108);
6549         assert(Date(-2008, 7, 6).diffMonths(dateBC) == -108);
6550         assert(Date(-2008, 7, 11).diffMonths(dateBC) == -108);
6551         assert(Date(-2008, 7, 16).diffMonths(dateBC) == -108);
6552         assert(Date(-2008, 7, 21).diffMonths(dateBC) == -108);
6553         assert(Date(-2008, 7, 26).diffMonths(dateBC) == -108);
6554         assert(Date(-2008, 7, 31).diffMonths(dateBC) == -108);
6555         assert(Date(-2008, 8, 1).diffMonths(dateBC) == -107);
6556
6557         // Test Both
6558         assert(Date(3, 3, 3).diffMonths(Date(-5, 5, 5)) == 94);
6559         assert(Date(-5, 5, 5).diffMonths(Date(3, 3, 3)) == -94);
6560
6561         const cdate = Date(1999, 7, 6);
6562         immutable idate = Date(1999, 7, 6);
6563         assert(date.diffMonths(date) == 0);
6564         assert(cdate.diffMonths(date) == 0);
6565         assert(idate.diffMonths(date) == 0);
6566
6567         assert(date.diffMonths(cdate) == 0);
6568         assert(cdate.diffMonths(cdate) == 0);
6569         assert(idate.diffMonths(cdate) == 0);
6570
6571         assert(date.diffMonths(idate) == 0);
6572         assert(cdate.diffMonths(idate) == 0);
6573         assert(idate.diffMonths(idate) == 0);
6574     }
6575
6576
6577     /++
6578         Whether this $(LREF Date) is in a leap year.
6579      +/
6580     @property bool isLeapYear() const @safe pure nothrow @nogc
6581     {
6582         return yearIsLeapYear(_year);
6583     }
6584
6585     @safe unittest
6586     {
6587         auto date = Date(1999, 7, 6);
6588         const cdate = Date(1999, 7, 6);
6589         immutable idate = Date(1999, 7, 6);
6590         static assert(!__traits(compiles, date.isLeapYear = true));
6591         static assert(!__traits(compiles, cdate.isLeapYear = true));
6592         static assert(!__traits(compiles, idate.isLeapYear = true));
6593     }
6594
6595
6596     /++
6597         Day of the week this $(LREF Date) is on.
6598       +/
6599     @property DayOfWeek dayOfWeek() const @safe pure nothrow @nogc
6600     {
6601         return getDayOfWeek(dayOfGregorianCal);
6602     }
6603
6604     @safe unittest
6605     {
6606         const cdate = Date(1999, 7, 6);
6607         immutable idate = Date(1999, 7, 6);
6608         assert(cdate.dayOfWeek == DayOfWeek.tue);
6609         static assert(!__traits(compiles, cdate.dayOfWeek = DayOfWeek.sun));
6610         assert(idate.dayOfWeek == DayOfWeek.tue);
6611         static assert(!__traits(compiles, idate.dayOfWeek = DayOfWeek.sun));
6612     }
6613
6614
6615     /++
6616         Day of the year this $(LREF Date) is on.
6617       +/
6618     @property ushort dayOfYear() const @safe pure nothrow @nogc
6619     {
6620         if (_month >= Month.jan && _month <= Month.dec)
6621         {
6622             immutable int[] lastDay = isLeapYear ? lastDayLeap : lastDayNonLeap;
6623             auto monthIndex = _month - Month.jan;
6624
6625             return cast(ushort)(lastDay[monthIndex] + _day);
6626         }
6627         assert(0, "Invalid month.");
6628     }
6629
6630     ///
6631     @safe unittest
6632     {
6633         assert(Date(1999, 1, 1).dayOfYear == 1);
6634         assert(Date(1999, 12, 31).dayOfYear == 365);
6635         assert(Date(2000, 12, 31).dayOfYear == 366);
6636     }
6637
6638     @safe unittest
6639     {
6640         import std.algorithm.iteration : filter;
6641         import std.range : chain;
6642
6643         foreach (year; filter!((a){return !yearIsLeapYear(a);})(chain(testYearsBC, testYearsAD)))
6644         {
6645             foreach (doy; testDaysOfYear)
6646                 assert(Date(year, doy.md.month, doy.md.day).dayOfYear == doy.day);
6647         }
6648
6649         foreach (year; filter!((a){return yearIsLeapYear(a);})(chain(testYearsBC, testYearsAD)))
6650         {
6651             foreach (doy; testDaysOfLeapYear)
6652                 assert(Date(year, doy.md.month, doy.md.day).dayOfYear == doy.day);
6653         }
6654
6655         const cdate = Date(1999, 7, 6);
6656         immutable idate = Date(1999, 7, 6);
6657         assert(cdate.dayOfYear == 187);
6658         assert(idate.dayOfYear == 187);
6659     }
6660
6661     /++
6662         Day of the year.
6663
6664         Params:
6665             day = The day of the year to set which day of the year this
6666                   $(LREF Date) is on.
6667
6668         Throws:
6669             $(REF DateTimeException,std,datetime,date) if the given day is an
6670             invalid day of the year.
6671       +/
6672     @property void dayOfYear(int day) @safe pure
6673     {
6674         setDayOfYear!true(day);
6675     }
6676
6677     private void setDayOfYear(bool useExceptions = false)(int day)
6678     {
6679         immutable int[] lastDay = isLeapYear ? lastDayLeap : lastDayNonLeap;
6680
6681         bool dayOutOfRange = day <= 0 || day > (isLeapYear ? daysInLeapYear : daysInYear);
6682         enum errorMsg = "Invalid day of the year.";
6683
6684         static if (useExceptions)
6685         {
6686             if (dayOutOfRange) throw new DateTimeException(errorMsg);
6687         }
6688         else
6689         {
6690             assert(!dayOutOfRange, errorMsg);
6691         }
6692
6693         foreach (i; 1 .. lastDay.length)
6694         {
6695             if (day <= lastDay[i])
6696             {
6697                 _month = cast(Month)(cast(int) Month.jan + i - 1);
6698                 _day = cast(ubyte)(day - lastDay[i - 1]);
6699                 return;
6700             }
6701         }
6702         assert(0, "Invalid day of the year.");
6703     }
6704
6705     @safe unittest
6706     {
6707         static void test(Date date, int day, MonthDay expected, size_t line = __LINE__)
6708         {
6709             date.dayOfYear = day;
6710             assert(date.month == expected.month);
6711             assert(date.day == expected.day);
6712         }
6713
6714         foreach (doy; testDaysOfYear)
6715         {
6716             test(Date(1999, 1, 1), doy.day, doy.md);
6717             test(Date(-1, 1, 1), doy.day, doy.md);
6718         }
6719
6720         foreach (doy; testDaysOfLeapYear)
6721         {
6722             test(Date(2000, 1, 1), doy.day, doy.md);
6723             test(Date(-4, 1, 1), doy.day, doy.md);
6724         }
6725
6726         const cdate = Date(1999, 7, 6);
6727         immutable idate = Date(1999, 7, 6);
6728         static assert(!__traits(compiles, cdate.dayOfYear = 187));
6729         static assert(!__traits(compiles, idate.dayOfYear = 187));
6730     }
6731
6732
6733     /++
6734         The Xth day of the Gregorian Calendar that this $(LREF Date) is on.
6735      +/
6736     @property int dayOfGregorianCal() const @safe pure nothrow @nogc
6737     {
6738         if (isAD)
6739         {
6740             if (_year == 1)
6741                 return dayOfYear;
6742
6743             int years = _year - 1;
6744             auto days = (years / 400) * daysIn400Years;
6745             years %= 400;
6746
6747             days += (years / 100) * daysIn100Years;
6748             years %= 100;
6749
6750             days += (years / 4) * daysIn4Years;
6751             years %= 4;
6752
6753             days += years * daysInYear;
6754
6755             days += dayOfYear;
6756
6757             return days;
6758         }
6759         else if (_year == 0)
6760             return dayOfYear - daysInLeapYear;
6761         else
6762         {
6763             int years = _year;
6764             auto days = (years / 400) * daysIn400Years;
6765             years %= 400;
6766
6767             days += (years / 100) * daysIn100Years;
6768             years %= 100;
6769
6770             days += (years / 4) * daysIn4Years;
6771             years %= 4;
6772
6773             if (years < 0)
6774             {
6775                 days -= daysInLeapYear;
6776                 ++years;
6777
6778                 days += years * daysInYear;
6779
6780                 days -= daysInYear - dayOfYear;
6781             }
6782             else
6783                 days -= daysInLeapYear - dayOfYear;
6784
6785             return days;
6786         }
6787     }
6788
6789     ///
6790     @safe unittest
6791     {
6792         assert(Date(1, 1, 1).dayOfGregorianCal == 1);
6793         assert(Date(1, 12, 31).dayOfGregorianCal == 365);
6794         assert(Date(2, 1, 1).dayOfGregorianCal == 366);
6795
6796         assert(Date(0, 12, 31).dayOfGregorianCal == 0);
6797         assert(Date(0, 1, 1).dayOfGregorianCal == -365);
6798         assert(Date(-1, 12, 31).dayOfGregorianCal == -366);
6799
6800         assert(Date(2000, 1, 1).dayOfGregorianCal == 730_120);
6801         assert(Date(2010, 12, 31).dayOfGregorianCal == 734_137);
6802     }
6803
6804     @safe unittest
6805     {
6806         import std.range : chain;
6807
6808         foreach (gd; chain(testGregDaysBC, testGregDaysAD))
6809             assert(gd.date.dayOfGregorianCal == gd.day);
6810
6811         auto date = Date(1999, 7, 6);
6812         const cdate = Date(1999, 7, 6);
6813         immutable idate = Date(1999, 7, 6);
6814         assert(date.dayOfGregorianCal == 729_941);
6815         assert(cdate.dayOfGregorianCal == 729_941);
6816         assert(idate.dayOfGregorianCal == 729_941);
6817     }
6818
6819     /++
6820         The Xth day of the Gregorian Calendar that this $(LREF Date) is on.
6821
6822         Params:
6823             day = The day of the Gregorian Calendar to set this $(LREF Date) to.
6824      +/
6825     @property void dayOfGregorianCal(int day) @safe pure nothrow @nogc
6826     {
6827         this = Date(day);
6828     }
6829
6830     ///
6831     @safe unittest
6832     {
6833         auto date = Date.init;
6834         date.dayOfGregorianCal = 1;
6835         assert(date == Date(1, 1, 1));
6836
6837         date.dayOfGregorianCal = 365;
6838         assert(date == Date(1, 12, 31));
6839
6840         date.dayOfGregorianCal = 366;
6841         assert(date == Date(2, 1, 1));
6842
6843         date.dayOfGregorianCal = 0;
6844         assert(date == Date(0, 12, 31));
6845
6846         date.dayOfGregorianCal = -365;
6847         assert(date == Date(-0, 1, 1));
6848
6849         date.dayOfGregorianCal = -366;
6850         assert(date == Date(-1, 12, 31));
6851
6852         date.dayOfGregorianCal = 730_120;
6853         assert(date == Date(2000, 1, 1));
6854
6855         date.dayOfGregorianCal = 734_137;
6856         assert(date == Date(2010, 12, 31));
6857     }
6858
6859     @safe unittest
6860     {
6861         auto date = Date(1999, 7, 6);
6862         const cdate = Date(1999, 7, 6);
6863         immutable idate = Date(1999, 7, 6);
6864         date.dayOfGregorianCal = 187;
6865         assert(date.dayOfGregorianCal == 187);
6866         static assert(!__traits(compiles, cdate.dayOfGregorianCal = 187));
6867         static assert(!__traits(compiles, idate.dayOfGregorianCal = 187));
6868     }
6869
6870
6871     /++
6872         The ISO 8601 week of the year that this $(LREF Date) is in.
6873
6874         See_Also:
6875             $(HTTP en.wikipedia.org/wiki/ISO_week_date, ISO Week Date)
6876       +/
6877     @property ubyte isoWeek() const @safe pure nothrow
6878     {
6879         immutable weekday = dayOfWeek;
6880         immutable adjustedWeekday = weekday == DayOfWeek.sun ? 7 : weekday;
6881         immutable week = (dayOfYear - adjustedWeekday + 10) / 7;
6882
6883         try
6884         {
6885             if (week == 53)
6886             {
6887                 switch (Date(_year + 1, 1, 1).dayOfWeek)
6888                 {
6889                     case DayOfWeek.mon:
6890                     case DayOfWeek.tue:
6891                     case DayOfWeek.wed:
6892                     case DayOfWeek.thu:
6893                         return 1;
6894                     case DayOfWeek.fri:
6895                     case DayOfWeek.sat:
6896                     case DayOfWeek.sun:
6897                         return 53;
6898                     default:
6899                         assert(0, "Invalid ISO Week");
6900                 }
6901             }
6902             else if (week > 0)
6903                 return cast(ubyte) week;
6904             else
6905                 return Date(_year - 1, 12, 31).isoWeek;
6906         }
6907         catch (Exception e)
6908             assert(0, "Date's constructor threw.");
6909     }
6910
6911     @safe unittest
6912     {
6913         // Test A.D.
6914         assert(Date(2009, 12, 28).isoWeek == 53);
6915         assert(Date(2009, 12, 29).isoWeek == 53);
6916         assert(Date(2009, 12, 30).isoWeek == 53);
6917         assert(Date(2009, 12, 31).isoWeek == 53);
6918         assert(Date(2010, 1, 1).isoWeek == 53);
6919         assert(Date(2010, 1, 2).isoWeek == 53);
6920         assert(Date(2010, 1, 3).isoWeek == 53);
6921         assert(Date(2010, 1, 4).isoWeek == 1);
6922         assert(Date(2010, 1, 5).isoWeek == 1);
6923         assert(Date(2010, 1, 6).isoWeek == 1);
6924         assert(Date(2010, 1, 7).isoWeek == 1);
6925         assert(Date(2010, 1, 8).isoWeek == 1);
6926         assert(Date(2010, 1, 9).isoWeek == 1);
6927         assert(Date(2010, 1, 10).isoWeek == 1);
6928         assert(Date(2010, 1, 11).isoWeek == 2);
6929         assert(Date(2010, 12, 31).isoWeek == 52);
6930
6931         assert(Date(2004, 12, 26).isoWeek == 52);
6932         assert(Date(2004, 12, 27).isoWeek == 53);
6933         assert(Date(2004, 12, 28).isoWeek == 53);
6934         assert(Date(2004, 12, 29).isoWeek == 53);
6935         assert(Date(2004, 12, 30).isoWeek == 53);
6936         assert(Date(2004, 12, 31).isoWeek == 53);
6937         assert(Date(2005, 1, 1).isoWeek == 53);
6938         assert(Date(2005, 1, 2).isoWeek == 53);
6939
6940         assert(Date(2005, 12, 31).isoWeek == 52);
6941         assert(Date(2007, 1, 1).isoWeek == 1);
6942
6943         assert(Date(2007, 12, 30).isoWeek == 52);
6944         assert(Date(2007, 12, 31).isoWeek == 1);
6945         assert(Date(2008, 1, 1).isoWeek == 1);
6946
6947         assert(Date(2008, 12, 28).isoWeek == 52);
6948         assert(Date(2008, 12, 29).isoWeek == 1);
6949         assert(Date(2008, 12, 30).isoWeek == 1);
6950         assert(Date(2008, 12, 31).isoWeek == 1);
6951         assert(Date(2009, 1, 1).isoWeek == 1);
6952         assert(Date(2009, 1, 2).isoWeek == 1);
6953         assert(Date(2009, 1, 3).isoWeek == 1);
6954         assert(Date(2009, 1, 4).isoWeek == 1);
6955
6956         // Test B.C.
6957         // The algorithm should work identically for both A.D. and B.C. since
6958         // it doesn't really take the year into account, so B.C. testing
6959         // probably isn't really needed.
6960         assert(Date(0, 12, 31).isoWeek == 52);
6961         assert(Date(0, 1, 4).isoWeek == 1);
6962         assert(Date(0, 1, 1).isoWeek == 52);
6963
6964         const cdate = Date(1999, 7, 6);
6965         immutable idate = Date(1999, 7, 6);
6966         assert(cdate.isoWeek == 27);
6967         static assert(!__traits(compiles, cdate.isoWeek = 3));
6968         assert(idate.isoWeek == 27);
6969         static assert(!__traits(compiles, idate.isoWeek = 3));
6970     }
6971
6972
6973     /++
6974         $(LREF Date) for the last day in the month that this $(LREF Date) is in.
6975       +/
6976     @property Date endOfMonth() const @safe pure nothrow
6977     {
6978         try
6979             return Date(_year, _month, maxDay(_year, _month));
6980         catch (Exception e)
6981             assert(0, "Date's constructor threw.");
6982     }
6983
6984     ///
6985     @safe unittest
6986     {
6987         assert(Date(1999, 1, 6).endOfMonth == Date(1999, 1, 31));
6988         assert(Date(1999, 2, 7).endOfMonth == Date(1999, 2, 28));
6989         assert(Date(2000, 2, 7).endOfMonth == Date(2000, 2, 29));
6990         assert(Date(2000, 6, 4).endOfMonth == Date(2000, 6, 30));
6991     }
6992
6993     @safe unittest
6994     {
6995         // Test A.D.
6996         assert(Date(1999, 1, 1).endOfMonth == Date(1999, 1, 31));
6997         assert(Date(1999, 2, 1).endOfMonth == Date(1999, 2, 28));
6998         assert(Date(2000, 2, 1).endOfMonth == Date(2000, 2, 29));
6999         assert(Date(1999, 3, 1).endOfMonth == Date(1999, 3, 31));
7000         assert(Date(1999, 4, 1).endOfMonth == Date(1999, 4, 30));
7001         assert(Date(1999, 5, 1).endOfMonth == Date(1999, 5, 31));
7002         assert(Date(1999, 6, 1).endOfMonth == Date(1999, 6, 30));
7003         assert(Date(1999, 7, 1).endOfMonth == Date(1999, 7, 31));
7004         assert(Date(1999, 8, 1).endOfMonth == Date(1999, 8, 31));
7005         assert(Date(1999, 9, 1).endOfMonth == Date(1999, 9, 30));
7006         assert(Date(1999, 10, 1).endOfMonth == Date(1999, 10, 31));
7007         assert(Date(1999, 11, 1).endOfMonth == Date(1999, 11, 30));
7008         assert(Date(1999, 12, 1).endOfMonth == Date(1999, 12, 31));
7009
7010         // Test B.C.
7011         assert(Date(-1999, 1, 1).endOfMonth == Date(-1999, 1, 31));
7012         assert(Date(-1999, 2, 1).endOfMonth == Date(-1999, 2, 28));
7013         assert(Date(-2000, 2, 1).endOfMonth == Date(-2000, 2, 29));
7014         assert(Date(-1999, 3, 1).endOfMonth == Date(-1999, 3, 31));
7015         assert(Date(-1999, 4, 1).endOfMonth == Date(-1999, 4, 30));
7016         assert(Date(-1999, 5, 1).endOfMonth == Date(-1999, 5, 31));
7017         assert(Date(-1999, 6, 1).endOfMonth == Date(-1999, 6, 30));
7018         assert(Date(-1999, 7, 1).endOfMonth == Date(-1999, 7, 31));
7019         assert(Date(-1999, 8, 1).endOfMonth == Date(-1999, 8, 31));
7020         assert(Date(-1999, 9, 1).endOfMonth == Date(-1999, 9, 30));
7021         assert(Date(-1999, 10, 1).endOfMonth == Date(-1999, 10, 31));
7022         assert(Date(-1999, 11, 1).endOfMonth == Date(-1999, 11, 30));
7023         assert(Date(-1999, 12, 1).endOfMonth == Date(-1999, 12, 31));
7024
7025         const cdate = Date(1999, 7, 6);
7026         immutable idate = Date(1999, 7, 6);
7027         static assert(!__traits(compiles, cdate.endOfMonth = Date(1999, 7, 30)));
7028         static assert(!__traits(compiles, idate.endOfMonth = Date(1999, 7, 30)));
7029     }
7030
7031
7032     /++
7033         The last day in the month that this $(LREF Date) is in.
7034       +/
7035     @property ubyte daysInMonth() const @safe pure nothrow @nogc
7036     {
7037         return maxDay(_year, _month);
7038     }
7039
7040     ///
7041     @safe unittest
7042     {
7043         assert(Date(1999, 1, 6).daysInMonth == 31);
7044         assert(Date(1999, 2, 7).daysInMonth == 28);
7045         assert(Date(2000, 2, 7).daysInMonth == 29);
7046         assert(Date(2000, 6, 4).daysInMonth == 30);
7047     }
7048
7049     @safe unittest
7050     {
7051         // Test A.D.
7052         assert(Date(1999, 1, 1).daysInMonth == 31);
7053         assert(Date(1999, 2, 1).daysInMonth == 28);
7054         assert(Date(2000, 2, 1).daysInMonth == 29);
7055         assert(Date(1999, 3, 1).daysInMonth == 31);
7056         assert(Date(1999, 4, 1).daysInMonth == 30);
7057         assert(Date(1999, 5, 1).daysInMonth == 31);
7058         assert(Date(1999, 6, 1).daysInMonth == 30);
7059         assert(Date(1999, 7, 1).daysInMonth == 31);
7060         assert(Date(1999, 8, 1).daysInMonth == 31);
7061         assert(Date(1999, 9, 1).daysInMonth == 30);
7062         assert(Date(1999, 10, 1).daysInMonth == 31);
7063         assert(Date(1999, 11, 1).daysInMonth == 30);
7064         assert(Date(1999, 12, 1).daysInMonth == 31);
7065
7066         // Test B.C.
7067         assert(Date(-1999, 1, 1).daysInMonth == 31);
7068         assert(Date(-1999, 2, 1).daysInMonth == 28);
7069         assert(Date(-2000, 2, 1).daysInMonth == 29);
7070         assert(Date(-1999, 3, 1).daysInMonth == 31);
7071         assert(Date(-1999, 4, 1).daysInMonth == 30);
7072         assert(Date(-1999, 5, 1).daysInMonth == 31);
7073         assert(Date(-1999, 6, 1).daysInMonth == 30);
7074         assert(Date(-1999, 7, 1).daysInMonth == 31);
7075         assert(Date(-1999, 8, 1).daysInMonth == 31);
7076         assert(Date(-1999, 9, 1).daysInMonth == 30);
7077         assert(Date(-1999, 10, 1).daysInMonth == 31);
7078         assert(Date(-1999, 11, 1).daysInMonth == 30);
7079         assert(Date(-1999, 12, 1).daysInMonth == 31);
7080
7081         const cdate = Date(1999, 7, 6);
7082         immutable idate = Date(1999, 7, 6);
7083         static assert(!__traits(compiles, cdate.daysInMonth = 30));
7084         static assert(!__traits(compiles, idate.daysInMonth = 30));
7085     }
7086
7087
7088     /++
7089         Whether the current year is a date in A.D.
7090       +/
7091     @property bool isAD() const @safe pure nothrow @nogc
7092     {
7093         return _year > 0;
7094     }
7095
7096     ///
7097     @safe unittest
7098     {
7099         assert(Date(1, 1, 1).isAD);
7100         assert(Date(2010, 12, 31).isAD);
7101         assert(!Date(0, 12, 31).isAD);
7102         assert(!Date(-2010, 1, 1).isAD);
7103     }
7104
7105     @safe unittest
7106     {
7107         assert(Date(2010, 7, 4).isAD);
7108         assert(Date(1, 1, 1).isAD);
7109         assert(!Date(0, 1, 1).isAD);
7110         assert(!Date(-1, 1, 1).isAD);
7111         assert(!Date(-2010, 7, 4).isAD);
7112
7113         const cdate = Date(1999, 7, 6);
7114         immutable idate = Date(1999, 7, 6);
7115         assert(cdate.isAD);
7116         assert(idate.isAD);
7117     }
7118
7119
7120     /++
7121         The $(HTTP en.wikipedia.org/wiki/Julian_day, Julian day) for this
7122         $(LREF Date) at noon (since the Julian day changes at noon).
7123       +/
7124     @property long julianDay() const @safe pure nothrow @nogc
7125     {
7126         return dayOfGregorianCal + 1_721_425;
7127     }
7128
7129     @safe unittest
7130     {
7131         assert(Date(-4713, 11, 24).julianDay == 0);
7132         assert(Date(0, 12, 31).julianDay == 1_721_425);
7133         assert(Date(1, 1, 1).julianDay == 1_721_426);
7134         assert(Date(1582, 10, 15).julianDay == 2_299_161);
7135         assert(Date(1858, 11, 17).julianDay == 2_400_001);
7136         assert(Date(1982, 1, 4).julianDay == 2_444_974);
7137         assert(Date(1996, 3, 31).julianDay == 2_450_174);
7138         assert(Date(2010, 8, 24).julianDay == 2_455_433);
7139
7140         const cdate = Date(1999, 7, 6);
7141         immutable idate = Date(1999, 7, 6);
7142         assert(cdate.julianDay == 2_451_366);
7143         assert(idate.julianDay == 2_451_366);
7144     }
7145
7146
7147     /++
7148         The modified $(HTTP en.wikipedia.org/wiki/Julian_day, Julian day) for
7149         any time on this date (since, the modified Julian day changes at
7150         midnight).
7151       +/
7152     @property long modJulianDay() const @safe pure nothrow @nogc
7153     {
7154         return julianDay - 2_400_001;
7155     }
7156
7157     @safe unittest
7158     {
7159         assert(Date(1858, 11, 17).modJulianDay == 0);
7160         assert(Date(2010, 8, 24).modJulianDay == 55_432);
7161
7162         const cdate = Date(1999, 7, 6);
7163         immutable idate = Date(1999, 7, 6);
7164         assert(cdate.modJulianDay == 51_365);
7165         assert(idate.modJulianDay == 51_365);
7166     }
7167
7168
7169     /++
7170         Converts this $(LREF Date) to a string with the format YYYYMMDD.
7171       +/
7172     string toISOString() const @safe pure nothrow
7173     {
7174         import std.format : format;
7175         try
7176         {
7177             if (_year >= 0)
7178             {
7179                 if (_year < 10_000)
7180                     return format("%04d%02d%02d", _year, _month, _day);
7181                 else
7182                     return format("+%05d%02d%02d", _year, _month, _day);
7183             }
7184             else if (_year > -10_000)
7185                 return format("%05d%02d%02d", _year, _month, _day);
7186             else
7187                 return format("%06d%02d%02d", _year, _month, _day);
7188         }
7189         catch (Exception e)
7190             assert(0, "format() threw.");
7191     }
7192
7193     ///
7194     @safe unittest
7195     {
7196         assert(Date(2010, 7, 4).toISOString() == "20100704");
7197         assert(Date(1998, 12, 25).toISOString() == "19981225");
7198         assert(Date(0, 1, 5).toISOString() == "00000105");
7199         assert(Date(-4, 1, 5).toISOString() == "-00040105");
7200     }
7201
7202     @safe unittest
7203     {
7204         // Test A.D.
7205         assert(Date(9, 12, 4).toISOString() == "00091204");
7206         assert(Date(99, 12, 4).toISOString() == "00991204");
7207         assert(Date(999, 12, 4).toISOString() == "09991204");
7208         assert(Date(9999, 7, 4).toISOString() == "99990704");
7209         assert(Date(10000, 10, 20).toISOString() == "+100001020");
7210
7211         // Test B.C.
7212         assert(Date(0, 12, 4).toISOString() == "00001204");
7213         assert(Date(-9, 12, 4).toISOString() == "-00091204");
7214         assert(Date(-99, 12, 4).toISOString() == "-00991204");
7215         assert(Date(-999, 12, 4).toISOString() == "-09991204");
7216         assert(Date(-9999, 7, 4).toISOString() == "-99990704");
7217         assert(Date(-10000, 10, 20).toISOString() == "-100001020");
7218
7219         const cdate = Date(1999, 7, 6);
7220         immutable idate = Date(1999, 7, 6);
7221         assert(cdate.toISOString() == "19990706");
7222         assert(idate.toISOString() == "19990706");
7223     }
7224
7225     /++
7226         Converts this $(LREF Date) to a string with the format YYYY-MM-DD.
7227       +/
7228     string toISOExtString() const @safe pure nothrow
7229     {
7230         import std.format : format;
7231         try
7232         {
7233             if (_year >= 0)
7234             {
7235                 if (_year < 10_000)
7236                     return format("%04d-%02d-%02d", _year, _month, _day);
7237                 else
7238                     return format("+%05d-%02d-%02d", _year, _month, _day);
7239             }
7240             else if (_year > -10_000)
7241                 return format("%05d-%02d-%02d", _year, _month, _day);
7242             else
7243                 return format("%06d-%02d-%02d", _year, _month, _day);
7244         }
7245         catch (Exception e)
7246             assert(0, "format() threw.");
7247     }
7248
7249     ///
7250     @safe unittest
7251     {
7252         assert(Date(2010, 7, 4).toISOExtString() == "2010-07-04");
7253         assert(Date(1998, 12, 25).toISOExtString() == "1998-12-25");
7254         assert(Date(0, 1, 5).toISOExtString() == "0000-01-05");
7255         assert(Date(-4, 1, 5).toISOExtString() == "-0004-01-05");
7256     }
7257
7258     @safe unittest
7259     {
7260         // Test A.D.
7261         assert(Date(9, 12, 4).toISOExtString() == "0009-12-04");
7262         assert(Date(99, 12, 4).toISOExtString() == "0099-12-04");
7263         assert(Date(999, 12, 4).toISOExtString() == "0999-12-04");
7264         assert(Date(9999, 7, 4).toISOExtString() == "9999-07-04");
7265         assert(Date(10000, 10, 20).toISOExtString() == "+10000-10-20");
7266
7267         // Test B.C.
7268         assert(Date(0, 12, 4).toISOExtString() == "0000-12-04");
7269         assert(Date(-9, 12, 4).toISOExtString() == "-0009-12-04");
7270         assert(Date(-99, 12, 4).toISOExtString() == "-0099-12-04");
7271         assert(Date(-999, 12, 4).toISOExtString() == "-0999-12-04");
7272         assert(Date(-9999, 7, 4).toISOExtString() == "-9999-07-04");
7273         assert(Date(-10000, 10, 20).toISOExtString() == "-10000-10-20");
7274
7275         const cdate = Date(1999, 7, 6);
7276         immutable idate = Date(1999, 7, 6);
7277         assert(cdate.toISOExtString() == "1999-07-06");
7278         assert(idate.toISOExtString() == "1999-07-06");
7279     }
7280
7281     /++
7282         Converts this $(LREF Date) to a string with the format YYYY-Mon-DD.
7283       +/
7284     string toSimpleString() const @safe pure nothrow
7285     {
7286         import std.format : format;
7287         try
7288         {
7289             if (_year >= 0)
7290             {
7291                 if (_year < 10_000)
7292                     return format("%04d-%s-%02d", _year, monthToString(_month), _day);
7293                 else
7294                     return format("+%05d-%s-%02d", _year, monthToString(_month), _day);
7295             }
7296             else if (_year > -10_000)
7297                 return format("%05d-%s-%02d", _year, monthToString(_month), _day);
7298             else
7299                 return format("%06d-%s-%02d", _year, monthToString(_month), _day);
7300         }
7301         catch (Exception e)
7302             assert(0, "format() threw.");
7303     }
7304
7305     ///
7306     @safe unittest
7307     {
7308         assert(Date(2010, 7, 4).toSimpleString() == "2010-Jul-04");
7309         assert(Date(1998, 12, 25).toSimpleString() == "1998-Dec-25");
7310         assert(Date(0, 1, 5).toSimpleString() == "0000-Jan-05");
7311         assert(Date(-4, 1, 5).toSimpleString() == "-0004-Jan-05");
7312     }
7313
7314     @safe unittest
7315     {
7316         // Test A.D.
7317         assert(Date(9, 12, 4).toSimpleString() == "0009-Dec-04");
7318         assert(Date(99, 12, 4).toSimpleString() == "0099-Dec-04");
7319         assert(Date(999, 12, 4).toSimpleString() == "0999-Dec-04");
7320         assert(Date(9999, 7, 4).toSimpleString() == "9999-Jul-04");
7321         assert(Date(10000, 10, 20).toSimpleString() == "+10000-Oct-20");
7322
7323         // Test B.C.
7324         assert(Date(0, 12, 4).toSimpleString() == "0000-Dec-04");
7325         assert(Date(-9, 12, 4).toSimpleString() == "-0009-Dec-04");
7326         assert(Date(-99, 12, 4).toSimpleString() == "-0099-Dec-04");
7327         assert(Date(-999, 12, 4).toSimpleString() == "-0999-Dec-04");
7328         assert(Date(-9999, 7, 4).toSimpleString() == "-9999-Jul-04");
7329         assert(Date(-10000, 10, 20).toSimpleString() == "-10000-Oct-20");
7330
7331         const cdate = Date(1999, 7, 6);
7332         immutable idate = Date(1999, 7, 6);
7333         assert(cdate.toSimpleString() == "1999-Jul-06");
7334         assert(idate.toSimpleString() == "1999-Jul-06");
7335     }
7336
7337
7338     /++
7339         Converts this $(LREF Date) to a string.
7340
7341         This function exists to make it easy to convert a $(LREF Date) to a
7342         string for code that does not care what the exact format is - just that
7343         it presents the information in a clear manner. It also makes it easy to
7344         simply convert a $(LREF Date) to a string when using functions such as
7345         `to!string`, `format`, or `writeln` which use toString to convert
7346         user-defined types. So, it is unlikely that much code will call
7347         toString directly.
7348
7349         The format of the string is purposefully unspecified, and code that
7350         cares about the format of the string should use `toISOString`,
7351         `toISOExtString`, `toSimpleString`, or some other custom formatting
7352         function that explicitly generates the format that the code needs. The
7353         reason is that the code is then clear about what format it's using,
7354         making it less error-prone to maintain the code and interact with other
7355         software that consumes the generated strings. It's for this same reason
7356         $(LREF Date) has no `fromString` function, whereas it does have
7357         `fromISOString`, `fromISOExtString`, and `fromSimpleString`.
7358
7359         The format returned by toString may or may not change in the future.
7360       +/
7361     string toString() const @safe pure nothrow
7362     {
7363         return toSimpleString();
7364     }
7365
7366     @safe unittest
7367     {
7368         auto date = Date(1999, 7, 6);
7369         const cdate = Date(1999, 7, 6);
7370         immutable idate = Date(1999, 7, 6);
7371         assert(date.toString());
7372         assert(cdate.toString());
7373         assert(idate.toString());
7374     }
7375
7376
7377     /++
7378         Creates a $(LREF Date) from a string with the format YYYYMMDD. Whitespace
7379         is stripped from the given string.
7380
7381         Params:
7382             isoString = A string formatted in the ISO format for dates.
7383
7384         Throws:
7385             $(REF DateTimeException,std,datetime,date) if the given string is
7386             not in the ISO format or if the resulting $(LREF Date) would not be
7387             valid.
7388       +/
7389     static Date fromISOString(S)(in S isoString) @safe pure
7390         if (isSomeString!S)
7391     {
7392         import std.algorithm.searching : startsWith;
7393         import std.conv : to, text, ConvException;
7394         import std.exception : enforce;
7395         import std.string : strip;
7396
7397         auto str = isoString.strip;
7398
7399         enforce!DateTimeException(str.length >= 8, text("Invalid ISO String: ", isoString));
7400
7401         int day, month, year;
7402         auto yearStr = str[0 .. $ - 4];
7403
7404         try
7405         {
7406             // using conversion to uint plus cast because it checks for +/-
7407             // for us quickly while throwing ConvException
7408             day = cast(int) to!uint(str[$ - 2 .. $]);
7409             month = cast(int) to!uint(str[$ - 4 .. $ - 2]);
7410
7411             if (yearStr.length > 4)
7412             {
7413                 enforce!DateTimeException(yearStr.startsWith('-', '+'),
7414                         text("Invalid ISO String: ", isoString));
7415                 year = to!int(yearStr);
7416             }
7417             else
7418             {
7419                 year = cast(int) to!uint(yearStr);
7420             }
7421         }
7422         catch (ConvException)
7423         {
7424             throw new DateTimeException(text("Invalid ISO String: ", isoString));
7425         }
7426
7427         return Date(year, month, day);
7428     }
7429
7430     ///
7431     @safe unittest
7432     {
7433         assert(Date.fromISOString("20100704") == Date(2010, 7, 4));
7434         assert(Date.fromISOString("19981225") == Date(1998, 12, 25));
7435         assert(Date.fromISOString("00000105") == Date(0, 1, 5));
7436         assert(Date.fromISOString("-00040105") == Date(-4, 1, 5));
7437         assert(Date.fromISOString(" 20100704 ") == Date(2010, 7, 4));
7438     }
7439
7440     @safe unittest
7441     {
7442         assertThrown!DateTimeException(Date.fromISOString(""));
7443         assertThrown!DateTimeException(Date.fromISOString("990704"));
7444         assertThrown!DateTimeException(Date.fromISOString("0100704"));
7445         assertThrown!DateTimeException(Date.fromISOString("2010070"));
7446         assertThrown!DateTimeException(Date.fromISOString("2010070 "));
7447         assertThrown!DateTimeException(Date.fromISOString("120100704"));
7448         assertThrown!DateTimeException(Date.fromISOString("-0100704"));
7449         assertThrown!DateTimeException(Date.fromISOString("+0100704"));
7450         assertThrown!DateTimeException(Date.fromISOString("2010070a"));
7451         assertThrown!DateTimeException(Date.fromISOString("20100a04"));
7452         assertThrown!DateTimeException(Date.fromISOString("2010a704"));
7453
7454         assertThrown!DateTimeException(Date.fromISOString("99-07-04"));
7455         assertThrown!DateTimeException(Date.fromISOString("010-07-04"));
7456         assertThrown!DateTimeException(Date.fromISOString("2010-07-0"));
7457         assertThrown!DateTimeException(Date.fromISOString("2010-07-0 "));
7458         assertThrown!DateTimeException(Date.fromISOString("12010-07-04"));
7459         assertThrown!DateTimeException(Date.fromISOString("-010-07-04"));
7460         assertThrown!DateTimeException(Date.fromISOString("+010-07-04"));
7461         assertThrown!DateTimeException(Date.fromISOString("2010-07-0a"));
7462         assertThrown!DateTimeException(Date.fromISOString("2010-0a-04"));
7463         assertThrown!DateTimeException(Date.fromISOString("2010-a7-04"));
7464         assertThrown!DateTimeException(Date.fromISOString("2010/07/04"));
7465         assertThrown!DateTimeException(Date.fromISOString("2010/7/04"));
7466         assertThrown!DateTimeException(Date.fromISOString("2010/7/4"));
7467         assertThrown!DateTimeException(Date.fromISOString("2010/07/4"));
7468         assertThrown!DateTimeException(Date.fromISOString("2010-7-04"));
7469         assertThrown!DateTimeException(Date.fromISOString("2010-7-4"));
7470         assertThrown!DateTimeException(Date.fromISOString("2010-07-4"));
7471
7472         assertThrown!DateTimeException(Date.fromISOString("99Jul04"));
7473         assertThrown!DateTimeException(Date.fromISOString("010Jul04"));
7474         assertThrown!DateTimeException(Date.fromISOString("2010Jul0"));
7475         assertThrown!DateTimeException(Date.fromISOString("2010Jul0 "));
7476         assertThrown!DateTimeException(Date.fromISOString("12010Jul04"));
7477         assertThrown!DateTimeException(Date.fromISOString("-010Jul04"));
7478         assertThrown!DateTimeException(Date.fromISOString("+010Jul04"));
7479         assertThrown!DateTimeException(Date.fromISOString("2010Jul0a"));
7480         assertThrown!DateTimeException(Date.fromISOString("2010Jua04"));
7481         assertThrown!DateTimeException(Date.fromISOString("2010aul04"));
7482
7483         assertThrown!DateTimeException(Date.fromISOString("99-Jul-04"));
7484         assertThrown!DateTimeException(Date.fromISOString("010-Jul-04"));
7485         assertThrown!DateTimeException(Date.fromISOString("2010-Jul-0"));
7486         assertThrown!DateTimeException(Date.fromISOString("2010-Jul-0 "));
7487         assertThrown!DateTimeException(Date.fromISOString("12010-Jul-04"));
7488         assertThrown!DateTimeException(Date.fromISOString("-010-Jul-04"));
7489         assertThrown!DateTimeException(Date.fromISOString("+010-Jul-04"));
7490         assertThrown!DateTimeException(Date.fromISOString("2010-Jul-0a"));
7491         assertThrown!DateTimeException(Date.fromISOString("2010-Jua-04"));
7492         assertThrown!DateTimeException(Date.fromISOString("2010-Jal-04"));
7493         assertThrown!DateTimeException(Date.fromISOString("2010-aul-04"));
7494
7495         assertThrown!DateTimeException(Date.fromISOString("2010-07-04"));
7496         assertThrown!DateTimeException(Date.fromISOString("2010-Jul-04"));
7497
7498         assert(Date.fromISOString("19990706") == Date(1999, 7, 6));
7499         assert(Date.fromISOString("-19990706") == Date(-1999, 7, 6));
7500         assert(Date.fromISOString("+019990706") == Date(1999, 7, 6));
7501         assert(Date.fromISOString("19990706 ") == Date(1999, 7, 6));
7502         assert(Date.fromISOString(" 19990706") == Date(1999, 7, 6));
7503         assert(Date.fromISOString(" 19990706 ") == Date(1999, 7, 6));
7504     }
7505
7506     // bug# 17801
7507     @safe unittest
7508     {
7509         import std.conv : to;
7510         import std.meta : AliasSeq;
7511         foreach (C; AliasSeq!(char, wchar, dchar))
7512         {
7513             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
7514                 assert(Date.fromISOString(to!S("20121221")) == Date(2012, 12, 21));
7515         }
7516     }
7517
7518
7519     /++
7520         Creates a $(LREF Date) from a string with the format YYYY-MM-DD.
7521         Whitespace is stripped from the given string.
7522
7523         Params:
7524             isoExtString = A string formatted in the ISO Extended format for
7525                            dates.
7526
7527         Throws:
7528             $(REF DateTimeException,std,datetime,date) if the given string is
7529             not in the ISO Extended format or if the resulting $(LREF Date)
7530             would not be valid.
7531       +/
7532     static Date fromISOExtString(S)(in S isoExtString) @safe pure
7533         if (isSomeString!(S))
7534     {
7535         import std.algorithm.searching : all, startsWith;
7536         import std.ascii : isDigit;
7537         import std.conv : to;
7538         import std.exception : enforce;
7539         import std.format : format;
7540         import std.string : strip;
7541
7542         auto dstr = to!dstring(strip(isoExtString));
7543
7544         enforce(dstr.length >= 10, new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7545
7546         auto day = dstr[$-2 .. $];
7547         auto month = dstr[$-5 .. $-3];
7548         auto year = dstr[0 .. $-6];
7549
7550         enforce(dstr[$-3] == '-', new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7551         enforce(dstr[$-6] == '-', new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7552         enforce(all!isDigit(day),
7553                 new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7554         enforce(all!isDigit(month),
7555                 new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7556
7557         if (year.length > 4)
7558         {
7559             enforce(year.startsWith('-', '+'),
7560                     new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7561             enforce(all!isDigit(year[1..$]),
7562                     new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7563         }
7564         else
7565             enforce(all!isDigit(year),
7566                     new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
7567
7568         return Date(to!short(year), to!ubyte(month), to!ubyte(day));
7569     }
7570
7571     ///
7572     @safe unittest
7573     {
7574         assert(Date.fromISOExtString("2010-07-04") == Date(2010, 7, 4));
7575         assert(Date.fromISOExtString("1998-12-25") == Date(1998, 12, 25));
7576         assert(Date.fromISOExtString("0000-01-05") == Date(0, 1, 5));
7577         assert(Date.fromISOExtString("-0004-01-05") == Date(-4, 1, 5));
7578         assert(Date.fromISOExtString(" 2010-07-04 ") == Date(2010, 7, 4));
7579     }
7580
7581     @safe unittest
7582     {
7583         assertThrown!DateTimeException(Date.fromISOExtString(""));
7584         assertThrown!DateTimeException(Date.fromISOExtString("990704"));
7585         assertThrown!DateTimeException(Date.fromISOExtString("0100704"));
7586         assertThrown!DateTimeException(Date.fromISOExtString("2010070"));
7587         assertThrown!DateTimeException(Date.fromISOExtString("2010070 "));
7588         assertThrown!DateTimeException(Date.fromISOExtString("120100704"));
7589         assertThrown!DateTimeException(Date.fromISOExtString("-0100704"));
7590         assertThrown!DateTimeException(Date.fromISOExtString("+0100704"));
7591         assertThrown!DateTimeException(Date.fromISOExtString("2010070a"));
7592         assertThrown!DateTimeException(Date.fromISOExtString("20100a04"));
7593         assertThrown!DateTimeException(Date.fromISOExtString("2010a704"));
7594
7595         assertThrown!DateTimeException(Date.fromISOExtString("99-07-04"));
7596         assertThrown!DateTimeException(Date.fromISOExtString("010-07-04"));
7597         assertThrown!DateTimeException(Date.fromISOExtString("2010-07-0"));
7598         assertThrown!DateTimeException(Date.fromISOExtString("2010-07-0 "));
7599         assertThrown!DateTimeException(Date.fromISOExtString("12010-07-04"));
7600         assertThrown!DateTimeException(Date.fromISOExtString("-010-07-04"));
7601         assertThrown!DateTimeException(Date.fromISOExtString("+010-07-04"));
7602         assertThrown!DateTimeException(Date.fromISOExtString("2010-07-0a"));
7603         assertThrown!DateTimeException(Date.fromISOExtString("2010-0a-04"));
7604         assertThrown!DateTimeException(Date.fromISOExtString("2010-a7-04"));
7605         assertThrown!DateTimeException(Date.fromISOExtString("2010/07/04"));
7606         assertThrown!DateTimeException(Date.fromISOExtString("2010/7/04"));
7607         assertThrown!DateTimeException(Date.fromISOExtString("2010/7/4"));
7608         assertThrown!DateTimeException(Date.fromISOExtString("2010/07/4"));
7609         assertThrown!DateTimeException(Date.fromISOExtString("2010-7-04"));
7610         assertThrown!DateTimeException(Date.fromISOExtString("2010-7-4"));
7611         assertThrown!DateTimeException(Date.fromISOExtString("2010-07-4"));
7612
7613         assertThrown!DateTimeException(Date.fromISOExtString("99Jul04"));
7614         assertThrown!DateTimeException(Date.fromISOExtString("010Jul04"));
7615         assertThrown!DateTimeException(Date.fromISOExtString("2010Jul0"));
7616         assertThrown!DateTimeException(Date.fromISOExtString("2010-Jul-0 "));
7617         assertThrown!DateTimeException(Date.fromISOExtString("12010Jul04"));
7618         assertThrown!DateTimeException(Date.fromISOExtString("-010Jul04"));
7619         assertThrown!DateTimeException(Date.fromISOExtString("+010Jul04"));
7620         assertThrown!DateTimeException(Date.fromISOExtString("2010Jul0a"));
7621         assertThrown!DateTimeException(Date.fromISOExtString("2010Jua04"));
7622         assertThrown!DateTimeException(Date.fromISOExtString("2010aul04"));
7623
7624         assertThrown!DateTimeException(Date.fromISOExtString("99-Jul-04"));
7625         assertThrown!DateTimeException(Date.fromISOExtString("010-Jul-04"));
7626         assertThrown!DateTimeException(Date.fromISOExtString("2010-Jul-0"));
7627         assertThrown!DateTimeException(Date.fromISOExtString("2010Jul0 "));
7628         assertThrown!DateTimeException(Date.fromISOExtString("12010-Jul-04"));
7629         assertThrown!DateTimeException(Date.fromISOExtString("-010-Jul-04"));
7630         assertThrown!DateTimeException(Date.fromISOExtString("+010-Jul-04"));
7631         assertThrown!DateTimeException(Date.fromISOExtString("2010-Jul-0a"));
7632         assertThrown!DateTimeException(Date.fromISOExtString("2010-Jua-04"));
7633         assertThrown!DateTimeException(Date.fromISOExtString("2010-Jal-04"));
7634         assertThrown!DateTimeException(Date.fromISOExtString("2010-aul-04"));
7635
7636         assertThrown!DateTimeException(Date.fromISOExtString("20100704"));
7637         assertThrown!DateTimeException(Date.fromISOExtString("2010-Jul-04"));
7638
7639         assert(Date.fromISOExtString("1999-07-06") == Date(1999, 7, 6));
7640         assert(Date.fromISOExtString("-1999-07-06") == Date(-1999, 7, 6));
7641         assert(Date.fromISOExtString("+01999-07-06") == Date(1999, 7, 6));
7642         assert(Date.fromISOExtString("1999-07-06 ") == Date(1999, 7, 6));
7643         assert(Date.fromISOExtString(" 1999-07-06") == Date(1999, 7, 6));
7644         assert(Date.fromISOExtString(" 1999-07-06 ") == Date(1999, 7, 6));
7645     }
7646
7647     // bug# 17801
7648     @safe unittest
7649     {
7650         import std.conv : to;
7651         import std.meta : AliasSeq;
7652         foreach (C; AliasSeq!(char, wchar, dchar))
7653         {
7654             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
7655                 assert(Date.fromISOExtString(to!S("2012-12-21")) == Date(2012, 12, 21));
7656         }
7657     }
7658
7659
7660     /++
7661         Creates a $(LREF Date) from a string with the format YYYY-Mon-DD.
7662         Whitespace is stripped from the given string.
7663
7664         Params:
7665             simpleString = A string formatted in the way that toSimpleString
7666                            formats dates.
7667
7668         Throws:
7669             $(REF DateTimeException,std,datetime,date) if the given string is
7670             not in the correct format or if the resulting $(LREF Date) would not
7671             be valid.
7672       +/
7673     static Date fromSimpleString(S)(in S simpleString) @safe pure
7674         if (isSomeString!(S))
7675     {
7676         import std.algorithm.searching : all, startsWith;
7677         import std.ascii : isDigit;
7678         import std.conv : to;
7679         import std.exception : enforce;
7680         import std.format : format;
7681         import std.string : strip;
7682
7683         auto dstr = to!dstring(strip(simpleString));
7684
7685         enforce(dstr.length >= 11, new DateTimeException(format("Invalid string format: %s", simpleString)));
7686
7687         auto day = dstr[$-2 .. $];
7688         auto month = monthFromString(to!string(dstr[$-6 .. $-3]));
7689         auto year = dstr[0 .. $-7];
7690
7691         enforce(dstr[$-3] == '-', new DateTimeException(format("Invalid string format: %s", simpleString)));
7692         enforce(dstr[$-7] == '-', new DateTimeException(format("Invalid string format: %s", simpleString)));
7693         enforce(all!isDigit(day), new DateTimeException(format("Invalid string format: %s", simpleString)));
7694
7695         if (year.length > 4)
7696         {
7697             enforce(year.startsWith('-', '+'),
7698                     new DateTimeException(format("Invalid string format: %s", simpleString)));
7699             enforce(all!isDigit(year[1..$]),
7700                     new DateTimeException(format("Invalid string format: %s", simpleString)));
7701         }
7702         else
7703             enforce(all!isDigit(year),
7704                     new DateTimeException(format("Invalid string format: %s", simpleString)));
7705
7706         return Date(to!short(year), month, to!ubyte(day));
7707     }
7708
7709     ///
7710     @safe unittest
7711     {
7712         assert(Date.fromSimpleString("2010-Jul-04") == Date(2010, 7, 4));
7713         assert(Date.fromSimpleString("1998-Dec-25") == Date(1998, 12, 25));
7714         assert(Date.fromSimpleString("0000-Jan-05") == Date(0, 1, 5));
7715         assert(Date.fromSimpleString("-0004-Jan-05") == Date(-4, 1, 5));
7716         assert(Date.fromSimpleString(" 2010-Jul-04 ") == Date(2010, 7, 4));
7717     }
7718
7719     @safe unittest
7720     {
7721         assertThrown!DateTimeException(Date.fromSimpleString(""));
7722         assertThrown!DateTimeException(Date.fromSimpleString("990704"));
7723         assertThrown!DateTimeException(Date.fromSimpleString("0100704"));
7724         assertThrown!DateTimeException(Date.fromSimpleString("2010070"));
7725         assertThrown!DateTimeException(Date.fromSimpleString("2010070 "));
7726         assertThrown!DateTimeException(Date.fromSimpleString("120100704"));
7727         assertThrown!DateTimeException(Date.fromSimpleString("-0100704"));
7728         assertThrown!DateTimeException(Date.fromSimpleString("+0100704"));
7729         assertThrown!DateTimeException(Date.fromSimpleString("2010070a"));
7730         assertThrown!DateTimeException(Date.fromSimpleString("20100a04"));
7731         assertThrown!DateTimeException(Date.fromSimpleString("2010a704"));
7732
7733         assertThrown!DateTimeException(Date.fromSimpleString("99-07-04"));
7734         assertThrown!DateTimeException(Date.fromSimpleString("010-07-04"));
7735         assertThrown!DateTimeException(Date.fromSimpleString("2010-07-0"));
7736         assertThrown!DateTimeException(Date.fromSimpleString("2010-07-0 "));
7737         assertThrown!DateTimeException(Date.fromSimpleString("12010-07-04"));
7738         assertThrown!DateTimeException(Date.fromSimpleString("-010-07-04"));
7739         assertThrown!DateTimeException(Date.fromSimpleString("+010-07-04"));
7740         assertThrown!DateTimeException(Date.fromSimpleString("2010-07-0a"));
7741         assertThrown!DateTimeException(Date.fromSimpleString("2010-0a-04"));
7742         assertThrown!DateTimeException(Date.fromSimpleString("2010-a7-04"));
7743         assertThrown!DateTimeException(Date.fromSimpleString("2010/07/04"));
7744         assertThrown!DateTimeException(Date.fromSimpleString("2010/7/04"));
7745         assertThrown!DateTimeException(Date.fromSimpleString("2010/7/4"));
7746         assertThrown!DateTimeException(Date.fromSimpleString("2010/07/4"));
7747         assertThrown!DateTimeException(Date.fromSimpleString("2010-7-04"));
7748         assertThrown!DateTimeException(Date.fromSimpleString("2010-7-4"));
7749         assertThrown!DateTimeException(Date.fromSimpleString("2010-07-4"));
7750
7751         assertThrown!DateTimeException(Date.fromSimpleString("99Jul04"));
7752         assertThrown!DateTimeException(Date.fromSimpleString("010Jul04"));
7753         assertThrown!DateTimeException(Date.fromSimpleString("2010Jul0"));
7754         assertThrown!DateTimeException(Date.fromSimpleString("2010Jul0 "));
7755         assertThrown!DateTimeException(Date.fromSimpleString("12010Jul04"));
7756         assertThrown!DateTimeException(Date.fromSimpleString("-010Jul04"));
7757         assertThrown!DateTimeException(Date.fromSimpleString("+010Jul04"));
7758         assertThrown!DateTimeException(Date.fromSimpleString("2010Jul0a"));
7759         assertThrown!DateTimeException(Date.fromSimpleString("2010Jua04"));
7760         assertThrown!DateTimeException(Date.fromSimpleString("2010aul04"));
7761
7762         assertThrown!DateTimeException(Date.fromSimpleString("99-Jul-04"));
7763         assertThrown!DateTimeException(Date.fromSimpleString("010-Jul-04"));
7764         assertThrown!DateTimeException(Date.fromSimpleString("2010-Jul-0"));
7765         assertThrown!DateTimeException(Date.fromSimpleString("2010-Jul-0 "));
7766         assertThrown!DateTimeException(Date.fromSimpleString("12010-Jul-04"));
7767         assertThrown!DateTimeException(Date.fromSimpleString("-010-Jul-04"));
7768         assertThrown!DateTimeException(Date.fromSimpleString("+010-Jul-04"));
7769         assertThrown!DateTimeException(Date.fromSimpleString("2010-Jul-0a"));
7770         assertThrown!DateTimeException(Date.fromSimpleString("2010-Jua-04"));
7771         assertThrown!DateTimeException(Date.fromSimpleString("2010-Jal-04"));
7772         assertThrown!DateTimeException(Date.fromSimpleString("2010-aul-04"));
7773
7774         assertThrown!DateTimeException(Date.fromSimpleString("20100704"));
7775         assertThrown!DateTimeException(Date.fromSimpleString("2010-07-04"));
7776
7777         assert(Date.fromSimpleString("1999-Jul-06") == Date(1999, 7, 6));
7778         assert(Date.fromSimpleString("-1999-Jul-06") == Date(-1999, 7, 6));
7779         assert(Date.fromSimpleString("+01999-Jul-06") == Date(1999, 7, 6));
7780         assert(Date.fromSimpleString("1999-Jul-06 ") == Date(1999, 7, 6));
7781         assert(Date.fromSimpleString(" 1999-Jul-06") == Date(1999, 7, 6));
7782         assert(Date.fromSimpleString(" 1999-Jul-06 ") == Date(1999, 7, 6));
7783     }
7784
7785     // bug# 17801
7786     @safe unittest
7787     {
7788         import std.conv : to;
7789         import std.meta : AliasSeq;
7790         foreach (C; AliasSeq!(char, wchar, dchar))
7791         {
7792             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
7793                 assert(Date.fromSimpleString(to!S("2012-Dec-21")) == Date(2012, 12, 21));
7794         }
7795     }
7796
7797
7798     /++
7799         Returns the $(LREF Date) farthest in the past which is representable by
7800         $(LREF Date).
7801       +/
7802     @property static Date min() @safe pure nothrow @nogc
7803     {
7804         auto date = Date.init;
7805         date._year = short.min;
7806         date._month = Month.jan;
7807         date._day = 1;
7808
7809         return date;
7810     }
7811
7812     @safe unittest
7813     {
7814         assert(Date.min.year < 0);
7815         assert(Date.min < Date.max);
7816     }
7817
7818
7819     /++
7820         Returns the $(LREF Date) farthest in the future which is representable
7821         by $(LREF Date).
7822       +/
7823     @property static Date max() @safe pure nothrow @nogc
7824     {
7825         auto date = Date.init;
7826         date._year = short.max;
7827         date._month = Month.dec;
7828         date._day = 31;
7829
7830         return date;
7831     }
7832
7833     @safe unittest
7834     {
7835         assert(Date.max.year > 0);
7836         assert(Date.max > Date.min);
7837     }
7838
7839
7840 private:
7841
7842     /+
7843         Whether the given values form a valid date.
7844
7845         Params:
7846             year  = The year to test.
7847             month = The month of the Gregorian Calendar to test.
7848             day   = The day of the month to test.
7849      +/
7850     static bool _valid(int year, int month, int day) @safe pure nothrow @nogc
7851     {
7852         if (!valid!"months"(month))
7853             return false;
7854         return valid!"days"(year, month, day);
7855     }
7856
7857
7858 package:
7859
7860     /+
7861         Adds the given number of days to this $(LREF Date). A negative number
7862         will subtract.
7863
7864         The month will be adjusted along with the day if the number of days
7865         added (or subtracted) would overflow (or underflow) the current month.
7866         The year will be adjusted along with the month if the increase (or
7867         decrease) to the month would cause it to overflow (or underflow) the
7868         current year.
7869
7870         $(D _addDays(numDays)) is effectively equivalent to
7871         $(D date.dayOfGregorianCal = date.dayOfGregorianCal + days).
7872
7873         Params:
7874             days = The number of days to add to this Date.
7875       +/
7876     ref Date _addDays(long days) return @safe pure nothrow @nogc
7877     {
7878         dayOfGregorianCal = cast(int)(dayOfGregorianCal + days);
7879         return this;
7880     }
7881
7882     @safe unittest
7883     {
7884         // Test A.D.
7885         {
7886             auto date = Date(1999, 2, 28);
7887             date._addDays(1);
7888             assert(date == Date(1999, 3, 1));
7889             date._addDays(-1);
7890             assert(date == Date(1999, 2, 28));
7891         }
7892
7893         {
7894             auto date = Date(2000, 2, 28);
7895             date._addDays(1);
7896             assert(date == Date(2000, 2, 29));
7897             date._addDays(1);
7898             assert(date == Date(2000, 3, 1));
7899             date._addDays(-1);
7900             assert(date == Date(2000, 2, 29));
7901         }
7902
7903         {
7904             auto date = Date(1999, 6, 30);
7905             date._addDays(1);
7906             assert(date == Date(1999, 7, 1));
7907             date._addDays(-1);
7908             assert(date == Date(1999, 6, 30));
7909         }
7910
7911         {
7912             auto date = Date(1999, 7, 31);
7913             date._addDays(1);
7914             assert(date == Date(1999, 8, 1));
7915             date._addDays(-1);
7916             assert(date == Date(1999, 7, 31));
7917         }
7918
7919         {
7920             auto date = Date(1999, 1, 1);
7921             date._addDays(-1);
7922             assert(date == Date(1998, 12, 31));
7923             date._addDays(1);
7924             assert(date == Date(1999, 1, 1));
7925         }
7926
7927         {
7928             auto date = Date(1999, 7, 6);
7929             date._addDays(9);
7930             assert(date == Date(1999, 7, 15));
7931             date._addDays(-11);
7932             assert(date == Date(1999, 7, 4));
7933             date._addDays(30);
7934             assert(date == Date(1999, 8, 3));
7935             date._addDays(-3);
7936             assert(date == Date(1999, 7, 31));
7937         }
7938
7939         {
7940             auto date = Date(1999, 7, 6);
7941             date._addDays(365);
7942             assert(date == Date(2000, 7, 5));
7943             date._addDays(-365);
7944             assert(date == Date(1999, 7, 6));
7945             date._addDays(366);
7946             assert(date == Date(2000, 7, 6));
7947             date._addDays(730);
7948             assert(date == Date(2002, 7, 6));
7949             date._addDays(-1096);
7950             assert(date == Date(1999, 7, 6));
7951         }
7952
7953         // Test B.C.
7954         {
7955             auto date = Date(-1999, 2, 28);
7956             date._addDays(1);
7957             assert(date == Date(-1999, 3, 1));
7958             date._addDays(-1);
7959             assert(date == Date(-1999, 2, 28));
7960         }
7961
7962         {
7963             auto date = Date(-2000, 2, 28);
7964             date._addDays(1);
7965             assert(date == Date(-2000, 2, 29));
7966             date._addDays(1);
7967             assert(date == Date(-2000, 3, 1));
7968             date._addDays(-1);
7969             assert(date == Date(-2000, 2, 29));
7970         }
7971
7972         {
7973             auto date = Date(-1999, 6, 30);
7974             date._addDays(1);
7975             assert(date == Date(-1999, 7, 1));
7976             date._addDays(-1);
7977             assert(date == Date(-1999, 6, 30));
7978         }
7979
7980         {
7981             auto date = Date(-1999, 7, 31);
7982             date._addDays(1);
7983             assert(date == Date(-1999, 8, 1));
7984             date._addDays(-1);
7985             assert(date == Date(-1999, 7, 31));
7986         }
7987
7988         {
7989             auto date = Date(-1999, 1, 1);
7990             date._addDays(-1);
7991             assert(date == Date(-2000, 12, 31));
7992             date._addDays(1);
7993             assert(date == Date(-1999, 1, 1));
7994         }
7995
7996         {
7997             auto date = Date(-1999, 7, 6);
7998             date._addDays(9);
7999             assert(date == Date(-1999, 7, 15));
8000             date._addDays(-11);
8001             assert(date == Date(-1999, 7, 4));
8002             date._addDays(30);
8003             assert(date == Date(-1999, 8, 3));
8004             date._addDays(-3);
8005         }
8006
8007         {
8008             auto date = Date(-1999, 7, 6);
8009             date._addDays(365);
8010             assert(date == Date(-1998, 7, 6));
8011             date._addDays(-365);
8012             assert(date == Date(-1999, 7, 6));
8013             date._addDays(366);
8014             assert(date == Date(-1998, 7, 7));
8015             date._addDays(730);
8016             assert(date == Date(-1996, 7, 6));
8017             date._addDays(-1096);
8018             assert(date == Date(-1999, 7, 6));
8019         }
8020
8021         // Test Both
8022         {
8023             auto date = Date(1, 7, 6);
8024             date._addDays(-365);
8025             assert(date == Date(0, 7, 6));
8026             date._addDays(365);
8027             assert(date == Date(1, 7, 6));
8028             date._addDays(-731);
8029             assert(date == Date(-1, 7, 6));
8030             date._addDays(730);
8031             assert(date == Date(1, 7, 5));
8032         }
8033
8034         const cdate = Date(1999, 7, 6);
8035         immutable idate = Date(1999, 7, 6);
8036         static assert(!__traits(compiles, cdate._addDays(12)));
8037         static assert(!__traits(compiles, idate._addDays(12)));
8038     }
8039
8040
8041     @safe pure invariant()
8042     {
8043         import std.format : format;
8044         assert(valid!"months"(_month),
8045                format("Invariant Failure: year [%s] month [%s] day [%s]", _year, _month, _day));
8046         assert(valid!"days"(_year, _month, _day),
8047                format("Invariant Failure: year [%s] month [%s] day [%s]", _year, _month, _day));
8048     }
8049
8050     short _year  = 1;
8051     Month _month = Month.jan;
8052     ubyte _day   = 1;
8053 }
8054
8055
8056 /++
8057     Represents a time of day with hours, minutes, and seconds. It uses 24 hour
8058     time.
8059 +/
8060 struct TimeOfDay
8061 {
8062 public:
8063
8064     /++
8065         Params:
8066             hour   = Hour of the day [0 - 24$(RPAREN).
8067             minute = Minute of the hour [0 - 60$(RPAREN).
8068             second = Second of the minute [0 - 60$(RPAREN).
8069
8070         Throws:
8071             $(REF DateTimeException,std,datetime,date) if the resulting
8072             $(LREF TimeOfDay) would be not be valid.
8073      +/
8074     this(int hour, int minute, int second = 0) @safe pure
8075     {
8076         enforceValid!"hours"(hour);
8077         enforceValid!"minutes"(minute);
8078         enforceValid!"seconds"(second);
8079
8080         _hour   = cast(ubyte) hour;
8081         _minute = cast(ubyte) minute;
8082         _second = cast(ubyte) second;
8083     }
8084
8085     @safe unittest
8086     {
8087         assert(TimeOfDay(0, 0) == TimeOfDay.init);
8088
8089         {
8090             auto tod = TimeOfDay(0, 0);
8091             assert(tod._hour == 0);
8092             assert(tod._minute == 0);
8093             assert(tod._second == 0);
8094         }
8095
8096         {
8097             auto tod = TimeOfDay(12, 30, 33);
8098             assert(tod._hour == 12);
8099             assert(tod._minute == 30);
8100             assert(tod._second == 33);
8101         }
8102
8103         {
8104             auto tod = TimeOfDay(23, 59, 59);
8105             assert(tod._hour == 23);
8106             assert(tod._minute == 59);
8107             assert(tod._second == 59);
8108         }
8109
8110         assertThrown!DateTimeException(TimeOfDay(24, 0, 0));
8111         assertThrown!DateTimeException(TimeOfDay(0, 60, 0));
8112         assertThrown!DateTimeException(TimeOfDay(0, 0, 60));
8113     }
8114
8115
8116     /++
8117         Compares this $(LREF TimeOfDay) with the given $(LREF TimeOfDay).
8118
8119         Returns:
8120             $(BOOKTABLE,
8121             $(TR $(TD this &lt; rhs) $(TD &lt; 0))
8122             $(TR $(TD this == rhs) $(TD 0))
8123             $(TR $(TD this &gt; rhs) $(TD &gt; 0))
8124             )
8125      +/
8126     int opCmp(in TimeOfDay rhs) const @safe pure nothrow @nogc
8127     {
8128         if (_hour < rhs._hour)
8129             return -1;
8130         if (_hour > rhs._hour)
8131             return 1;
8132
8133         if (_minute < rhs._minute)
8134             return -1;
8135         if (_minute > rhs._minute)
8136             return 1;
8137
8138         if (_second < rhs._second)
8139             return -1;
8140         if (_second > rhs._second)
8141             return 1;
8142
8143         return 0;
8144     }
8145
8146     @safe unittest
8147     {
8148         assert(TimeOfDay(0, 0, 0).opCmp(TimeOfDay.init) == 0);
8149
8150         assert(TimeOfDay(0, 0, 0).opCmp(TimeOfDay(0, 0, 0)) == 0);
8151         assert(TimeOfDay(12, 0, 0).opCmp(TimeOfDay(12, 0, 0)) == 0);
8152         assert(TimeOfDay(0, 30, 0).opCmp(TimeOfDay(0, 30, 0)) == 0);
8153         assert(TimeOfDay(0, 0, 33).opCmp(TimeOfDay(0, 0, 33)) == 0);
8154
8155         assert(TimeOfDay(12, 30, 0).opCmp(TimeOfDay(12, 30, 0)) == 0);
8156         assert(TimeOfDay(12, 30, 33).opCmp(TimeOfDay(12, 30, 33)) == 0);
8157
8158         assert(TimeOfDay(0, 30, 33).opCmp(TimeOfDay(0, 30, 33)) == 0);
8159         assert(TimeOfDay(0, 0, 33).opCmp(TimeOfDay(0, 0, 33)) == 0);
8160
8161         assert(TimeOfDay(12, 30, 33).opCmp(TimeOfDay(13, 30, 33)) < 0);
8162         assert(TimeOfDay(13, 30, 33).opCmp(TimeOfDay(12, 30, 33)) > 0);
8163         assert(TimeOfDay(12, 30, 33).opCmp(TimeOfDay(12, 31, 33)) < 0);
8164         assert(TimeOfDay(12, 31, 33).opCmp(TimeOfDay(12, 30, 33)) > 0);
8165         assert(TimeOfDay(12, 30, 33).opCmp(TimeOfDay(12, 30, 34)) < 0);
8166         assert(TimeOfDay(12, 30, 34).opCmp(TimeOfDay(12, 30, 33)) > 0);
8167
8168         assert(TimeOfDay(13, 30, 33).opCmp(TimeOfDay(12, 30, 34)) > 0);
8169         assert(TimeOfDay(12, 30, 34).opCmp(TimeOfDay(13, 30, 33)) < 0);
8170         assert(TimeOfDay(13, 30, 33).opCmp(TimeOfDay(12, 31, 33)) > 0);
8171         assert(TimeOfDay(12, 31, 33).opCmp(TimeOfDay(13, 30, 33)) < 0);
8172
8173         assert(TimeOfDay(12, 31, 33).opCmp(TimeOfDay(12, 30, 34)) > 0);
8174         assert(TimeOfDay(12, 30, 34).opCmp(TimeOfDay(12, 31, 33)) < 0);
8175
8176         const ctod = TimeOfDay(12, 30, 33);
8177         immutable itod = TimeOfDay(12, 30, 33);
8178         assert(ctod.opCmp(itod) == 0);
8179         assert(itod.opCmp(ctod) == 0);
8180     }
8181
8182
8183     /++
8184         Hours past midnight.
8185      +/
8186     @property ubyte hour() const @safe pure nothrow @nogc
8187     {
8188         return _hour;
8189     }
8190
8191     @safe unittest
8192     {
8193         assert(TimeOfDay.init.hour == 0);
8194         assert(TimeOfDay(12, 0, 0).hour == 12);
8195
8196         const ctod = TimeOfDay(12, 0, 0);
8197         immutable itod = TimeOfDay(12, 0, 0);
8198         assert(ctod.hour == 12);
8199         assert(itod.hour == 12);
8200     }
8201
8202
8203     /++
8204         Hours past midnight.
8205
8206         Params:
8207             hour = The hour of the day to set this $(LREF TimeOfDay)'s hour to.
8208
8209         Throws:
8210             $(REF DateTimeException,std,datetime,date) if the given hour would
8211             result in an invalid $(LREF TimeOfDay).
8212      +/
8213     @property void hour(int hour) @safe pure
8214     {
8215         enforceValid!"hours"(hour);
8216         _hour = cast(ubyte) hour;
8217     }
8218
8219     @safe unittest
8220     {
8221         assertThrown!DateTimeException((){TimeOfDay(0, 0, 0).hour = 24;}());
8222
8223         auto tod = TimeOfDay(0, 0, 0);
8224         tod.hour = 12;
8225         assert(tod == TimeOfDay(12, 0, 0));
8226
8227         const ctod = TimeOfDay(0, 0, 0);
8228         immutable itod = TimeOfDay(0, 0, 0);
8229         static assert(!__traits(compiles, ctod.hour = 12));
8230         static assert(!__traits(compiles, itod.hour = 12));
8231     }
8232
8233
8234     /++
8235         Minutes past the hour.
8236      +/
8237     @property ubyte minute() const @safe pure nothrow @nogc
8238     {
8239         return _minute;
8240     }
8241
8242     @safe unittest
8243     {
8244         assert(TimeOfDay.init.minute == 0);
8245         assert(TimeOfDay(0, 30, 0).minute == 30);
8246
8247         const ctod = TimeOfDay(0, 30, 0);
8248         immutable itod = TimeOfDay(0, 30, 0);
8249         assert(ctod.minute == 30);
8250         assert(itod.minute == 30);
8251     }
8252
8253
8254     /++
8255         Minutes past the hour.
8256
8257         Params:
8258             minute = The minute to set this $(LREF TimeOfDay)'s minute to.
8259
8260         Throws:
8261             $(REF DateTimeException,std,datetime,date) if the given minute
8262             would result in an invalid $(LREF TimeOfDay).
8263      +/
8264     @property void minute(int minute) @safe pure
8265     {
8266         enforceValid!"minutes"(minute);
8267         _minute = cast(ubyte) minute;
8268     }
8269
8270     @safe unittest
8271     {
8272         assertThrown!DateTimeException((){TimeOfDay(0, 0, 0).minute = 60;}());
8273
8274         auto tod = TimeOfDay(0, 0, 0);
8275         tod.minute = 30;
8276         assert(tod == TimeOfDay(0, 30, 0));
8277
8278         const ctod = TimeOfDay(0, 0, 0);
8279         immutable itod = TimeOfDay(0, 0, 0);
8280         static assert(!__traits(compiles, ctod.minute = 30));
8281         static assert(!__traits(compiles, itod.minute = 30));
8282     }
8283
8284
8285     /++
8286         Seconds past the minute.
8287      +/
8288     @property ubyte second() const @safe pure nothrow @nogc
8289     {
8290         return _second;
8291     }
8292
8293     @safe unittest
8294     {
8295         assert(TimeOfDay.init.second == 0);
8296         assert(TimeOfDay(0, 0, 33).second == 33);
8297
8298         const ctod = TimeOfDay(0, 0, 33);
8299         immutable itod = TimeOfDay(0, 0, 33);
8300         assert(ctod.second == 33);
8301         assert(itod.second == 33);
8302     }
8303
8304
8305     /++
8306         Seconds past the minute.
8307
8308         Params:
8309             second = The second to set this $(LREF TimeOfDay)'s second to.
8310
8311         Throws:
8312             $(REF DateTimeException,std,datetime,date) if the given second
8313             would result in an invalid $(LREF TimeOfDay).
8314      +/
8315     @property void second(int second) @safe pure
8316     {
8317         enforceValid!"seconds"(second);
8318         _second = cast(ubyte) second;
8319     }
8320
8321     @safe unittest
8322     {
8323         assertThrown!DateTimeException((){TimeOfDay(0, 0, 0).second = 60;}());
8324
8325         auto tod = TimeOfDay(0, 0, 0);
8326         tod.second = 33;
8327         assert(tod == TimeOfDay(0, 0, 33));
8328
8329         const ctod = TimeOfDay(0, 0, 0);
8330         immutable itod = TimeOfDay(0, 0, 0);
8331         static assert(!__traits(compiles, ctod.second = 33));
8332         static assert(!__traits(compiles, itod.second = 33));
8333     }
8334
8335
8336     /++
8337         Adds the given number of units to this $(LREF TimeOfDay). A negative
8338         number will subtract.
8339
8340         The difference between rolling and adding is that rolling does not
8341         affect larger units. For instance, rolling a $(LREF TimeOfDay)
8342         one hours's worth of minutes gets the exact same
8343         $(LREF TimeOfDay).
8344
8345         Accepted units are $(D "hours"), $(D "minutes"), and $(D "seconds").
8346
8347         Params:
8348             units = The units to add.
8349             value = The number of $(D_PARAM units) to add to this
8350                     $(LREF TimeOfDay).
8351       +/
8352     ref TimeOfDay roll(string units)(long value) @safe pure nothrow @nogc
8353         if (units == "hours")
8354     {
8355         return this += dur!"hours"(value);
8356     }
8357
8358     ///
8359     @safe unittest
8360     {
8361         auto tod1 = TimeOfDay(7, 12, 0);
8362         tod1.roll!"hours"(1);
8363         assert(tod1 == TimeOfDay(8, 12, 0));
8364
8365         auto tod2 = TimeOfDay(7, 12, 0);
8366         tod2.roll!"hours"(-1);
8367         assert(tod2 == TimeOfDay(6, 12, 0));
8368
8369         auto tod3 = TimeOfDay(23, 59, 0);
8370         tod3.roll!"minutes"(1);
8371         assert(tod3 == TimeOfDay(23, 0, 0));
8372
8373         auto tod4 = TimeOfDay(0, 0, 0);
8374         tod4.roll!"minutes"(-1);
8375         assert(tod4 == TimeOfDay(0, 59, 0));
8376
8377         auto tod5 = TimeOfDay(23, 59, 59);
8378         tod5.roll!"seconds"(1);
8379         assert(tod5 == TimeOfDay(23, 59, 0));
8380
8381         auto tod6 = TimeOfDay(0, 0, 0);
8382         tod6.roll!"seconds"(-1);
8383         assert(tod6 == TimeOfDay(0, 0, 59));
8384     }
8385
8386     @safe unittest
8387     {
8388         auto tod = TimeOfDay(12, 27, 2);
8389         tod.roll!"hours"(22).roll!"hours"(-7);
8390         assert(tod == TimeOfDay(3, 27, 2));
8391
8392         const ctod = TimeOfDay(0, 0, 0);
8393         immutable itod = TimeOfDay(0, 0, 0);
8394         static assert(!__traits(compiles, ctod.roll!"hours"(53)));
8395         static assert(!__traits(compiles, itod.roll!"hours"(53)));
8396     }
8397
8398
8399     // Shares documentation with "hours" version.
8400     ref TimeOfDay roll(string units)(long value) @safe pure nothrow @nogc
8401         if (units == "minutes" || units == "seconds")
8402     {
8403         import std.format : format;
8404
8405         enum memberVarStr = units[0 .. $ - 1];
8406         value %= 60;
8407         mixin(format("auto newVal = cast(ubyte)(_%s) + value;", memberVarStr));
8408
8409         if (value < 0)
8410         {
8411             if (newVal < 0)
8412                 newVal += 60;
8413         }
8414         else if (newVal >= 60)
8415             newVal -= 60;
8416
8417         mixin(format("_%s = cast(ubyte) newVal;", memberVarStr));
8418         return this;
8419     }
8420
8421     // Test roll!"minutes"().
8422     @safe unittest
8423     {
8424         static void testTOD(TimeOfDay orig, int minutes, in TimeOfDay expected, size_t line = __LINE__)
8425         {
8426             orig.roll!"minutes"(minutes);
8427             assert(orig == expected);
8428         }
8429
8430         testTOD(TimeOfDay(12, 30, 33), 0, TimeOfDay(12, 30, 33));
8431         testTOD(TimeOfDay(12, 30, 33), 1, TimeOfDay(12, 31, 33));
8432         testTOD(TimeOfDay(12, 30, 33), 2, TimeOfDay(12, 32, 33));
8433         testTOD(TimeOfDay(12, 30, 33), 3, TimeOfDay(12, 33, 33));
8434         testTOD(TimeOfDay(12, 30, 33), 4, TimeOfDay(12, 34, 33));
8435         testTOD(TimeOfDay(12, 30, 33), 5, TimeOfDay(12, 35, 33));
8436         testTOD(TimeOfDay(12, 30, 33), 10, TimeOfDay(12, 40, 33));
8437         testTOD(TimeOfDay(12, 30, 33), 15, TimeOfDay(12, 45, 33));
8438         testTOD(TimeOfDay(12, 30, 33), 29, TimeOfDay(12, 59, 33));
8439         testTOD(TimeOfDay(12, 30, 33), 30, TimeOfDay(12, 0, 33));
8440         testTOD(TimeOfDay(12, 30, 33), 45, TimeOfDay(12, 15, 33));
8441         testTOD(TimeOfDay(12, 30, 33), 60, TimeOfDay(12, 30, 33));
8442         testTOD(TimeOfDay(12, 30, 33), 75, TimeOfDay(12, 45, 33));
8443         testTOD(TimeOfDay(12, 30, 33), 90, TimeOfDay(12, 0, 33));
8444         testTOD(TimeOfDay(12, 30, 33), 100, TimeOfDay(12, 10, 33));
8445
8446         testTOD(TimeOfDay(12, 30, 33), 689, TimeOfDay(12, 59, 33));
8447         testTOD(TimeOfDay(12, 30, 33), 690, TimeOfDay(12, 0, 33));
8448         testTOD(TimeOfDay(12, 30, 33), 691, TimeOfDay(12, 1, 33));
8449         testTOD(TimeOfDay(12, 30, 33), 960, TimeOfDay(12, 30, 33));
8450         testTOD(TimeOfDay(12, 30, 33), 1439, TimeOfDay(12, 29, 33));
8451         testTOD(TimeOfDay(12, 30, 33), 1440, TimeOfDay(12, 30, 33));
8452         testTOD(TimeOfDay(12, 30, 33), 1441, TimeOfDay(12, 31, 33));
8453         testTOD(TimeOfDay(12, 30, 33), 2880, TimeOfDay(12, 30, 33));
8454
8455         testTOD(TimeOfDay(12, 30, 33), -1, TimeOfDay(12, 29, 33));
8456         testTOD(TimeOfDay(12, 30, 33), -2, TimeOfDay(12, 28, 33));
8457         testTOD(TimeOfDay(12, 30, 33), -3, TimeOfDay(12, 27, 33));
8458         testTOD(TimeOfDay(12, 30, 33), -4, TimeOfDay(12, 26, 33));
8459         testTOD(TimeOfDay(12, 30, 33), -5, TimeOfDay(12, 25, 33));
8460         testTOD(TimeOfDay(12, 30, 33), -10, TimeOfDay(12, 20, 33));
8461         testTOD(TimeOfDay(12, 30, 33), -15, TimeOfDay(12, 15, 33));
8462         testTOD(TimeOfDay(12, 30, 33), -29, TimeOfDay(12, 1, 33));
8463         testTOD(TimeOfDay(12, 30, 33), -30, TimeOfDay(12, 0, 33));
8464         testTOD(TimeOfDay(12, 30, 33), -45, TimeOfDay(12, 45, 33));
8465         testTOD(TimeOfDay(12, 30, 33), -60, TimeOfDay(12, 30, 33));
8466         testTOD(TimeOfDay(12, 30, 33), -75, TimeOfDay(12, 15, 33));
8467         testTOD(TimeOfDay(12, 30, 33), -90, TimeOfDay(12, 0, 33));
8468         testTOD(TimeOfDay(12, 30, 33), -100, TimeOfDay(12, 50, 33));
8469
8470         testTOD(TimeOfDay(12, 30, 33), -749, TimeOfDay(12, 1, 33));
8471         testTOD(TimeOfDay(12, 30, 33), -750, TimeOfDay(12, 0, 33));
8472         testTOD(TimeOfDay(12, 30, 33), -751, TimeOfDay(12, 59, 33));
8473         testTOD(TimeOfDay(12, 30, 33), -960, TimeOfDay(12, 30, 33));
8474         testTOD(TimeOfDay(12, 30, 33), -1439, TimeOfDay(12, 31, 33));
8475         testTOD(TimeOfDay(12, 30, 33), -1440, TimeOfDay(12, 30, 33));
8476         testTOD(TimeOfDay(12, 30, 33), -1441, TimeOfDay(12, 29, 33));
8477         testTOD(TimeOfDay(12, 30, 33), -2880, TimeOfDay(12, 30, 33));
8478
8479         testTOD(TimeOfDay(12, 0, 33), 1, TimeOfDay(12, 1, 33));
8480         testTOD(TimeOfDay(12, 0, 33), 0, TimeOfDay(12, 0, 33));
8481         testTOD(TimeOfDay(12, 0, 33), -1, TimeOfDay(12, 59, 33));
8482
8483         testTOD(TimeOfDay(11, 59, 33), 1, TimeOfDay(11, 0, 33));
8484         testTOD(TimeOfDay(11, 59, 33), 0, TimeOfDay(11, 59, 33));
8485         testTOD(TimeOfDay(11, 59, 33), -1, TimeOfDay(11, 58, 33));
8486
8487         testTOD(TimeOfDay(0, 0, 33), 1, TimeOfDay(0, 1, 33));
8488         testTOD(TimeOfDay(0, 0, 33), 0, TimeOfDay(0, 0, 33));
8489         testTOD(TimeOfDay(0, 0, 33), -1, TimeOfDay(0, 59, 33));
8490
8491         testTOD(TimeOfDay(23, 59, 33), 1, TimeOfDay(23, 0, 33));
8492         testTOD(TimeOfDay(23, 59, 33), 0, TimeOfDay(23, 59, 33));
8493         testTOD(TimeOfDay(23, 59, 33), -1, TimeOfDay(23, 58, 33));
8494
8495         auto tod = TimeOfDay(12, 27, 2);
8496         tod.roll!"minutes"(97).roll!"minutes"(-102);
8497         assert(tod == TimeOfDay(12, 22, 2));
8498
8499         const ctod = TimeOfDay(0, 0, 0);
8500         immutable itod = TimeOfDay(0, 0, 0);
8501         static assert(!__traits(compiles, ctod.roll!"minutes"(7)));
8502         static assert(!__traits(compiles, itod.roll!"minutes"(7)));
8503     }
8504
8505     // Test roll!"seconds"().
8506     @safe unittest
8507     {
8508         static void testTOD(TimeOfDay orig, int seconds, in TimeOfDay expected, size_t line = __LINE__)
8509         {
8510             orig.roll!"seconds"(seconds);
8511             assert(orig == expected);
8512         }
8513
8514         testTOD(TimeOfDay(12, 30, 33), 0, TimeOfDay(12, 30, 33));
8515         testTOD(TimeOfDay(12, 30, 33), 1, TimeOfDay(12, 30, 34));
8516         testTOD(TimeOfDay(12, 30, 33), 2, TimeOfDay(12, 30, 35));
8517         testTOD(TimeOfDay(12, 30, 33), 3, TimeOfDay(12, 30, 36));
8518         testTOD(TimeOfDay(12, 30, 33), 4, TimeOfDay(12, 30, 37));
8519         testTOD(TimeOfDay(12, 30, 33), 5, TimeOfDay(12, 30, 38));
8520         testTOD(TimeOfDay(12, 30, 33), 10, TimeOfDay(12, 30, 43));
8521         testTOD(TimeOfDay(12, 30, 33), 15, TimeOfDay(12, 30, 48));
8522         testTOD(TimeOfDay(12, 30, 33), 26, TimeOfDay(12, 30, 59));
8523         testTOD(TimeOfDay(12, 30, 33), 27, TimeOfDay(12, 30, 0));
8524         testTOD(TimeOfDay(12, 30, 33), 30, TimeOfDay(12, 30, 3));
8525         testTOD(TimeOfDay(12, 30, 33), 59, TimeOfDay(12, 30, 32));
8526         testTOD(TimeOfDay(12, 30, 33), 60, TimeOfDay(12, 30, 33));
8527         testTOD(TimeOfDay(12, 30, 33), 61, TimeOfDay(12, 30, 34));
8528
8529         testTOD(TimeOfDay(12, 30, 33), 1766, TimeOfDay(12, 30, 59));
8530         testTOD(TimeOfDay(12, 30, 33), 1767, TimeOfDay(12, 30, 0));
8531         testTOD(TimeOfDay(12, 30, 33), 1768, TimeOfDay(12, 30, 1));
8532         testTOD(TimeOfDay(12, 30, 33), 2007, TimeOfDay(12, 30, 0));
8533         testTOD(TimeOfDay(12, 30, 33), 3599, TimeOfDay(12, 30, 32));
8534         testTOD(TimeOfDay(12, 30, 33), 3600, TimeOfDay(12, 30, 33));
8535         testTOD(TimeOfDay(12, 30, 33), 3601, TimeOfDay(12, 30, 34));
8536         testTOD(TimeOfDay(12, 30, 33), 7200, TimeOfDay(12, 30, 33));
8537
8538         testTOD(TimeOfDay(12, 30, 33), -1, TimeOfDay(12, 30, 32));
8539         testTOD(TimeOfDay(12, 30, 33), -2, TimeOfDay(12, 30, 31));
8540         testTOD(TimeOfDay(12, 30, 33), -3, TimeOfDay(12, 30, 30));
8541         testTOD(TimeOfDay(12, 30, 33), -4, TimeOfDay(12, 30, 29));
8542         testTOD(TimeOfDay(12, 30, 33), -5, TimeOfDay(12, 30, 28));
8543         testTOD(TimeOfDay(12, 30, 33), -10, TimeOfDay(12, 30, 23));
8544         testTOD(TimeOfDay(12, 30, 33), -15, TimeOfDay(12, 30, 18));
8545         testTOD(TimeOfDay(12, 30, 33), -33, TimeOfDay(12, 30, 0));
8546         testTOD(TimeOfDay(12, 30, 33), -34, TimeOfDay(12, 30, 59));
8547         testTOD(TimeOfDay(12, 30, 33), -35, TimeOfDay(12, 30, 58));
8548         testTOD(TimeOfDay(12, 30, 33), -59, TimeOfDay(12, 30, 34));
8549         testTOD(TimeOfDay(12, 30, 33), -60, TimeOfDay(12, 30, 33));
8550         testTOD(TimeOfDay(12, 30, 33), -61, TimeOfDay(12, 30, 32));
8551
8552         testTOD(TimeOfDay(12, 30, 0), 1, TimeOfDay(12, 30, 1));
8553         testTOD(TimeOfDay(12, 30, 0), 0, TimeOfDay(12, 30, 0));
8554         testTOD(TimeOfDay(12, 30, 0), -1, TimeOfDay(12, 30, 59));
8555
8556         testTOD(TimeOfDay(12, 0, 0), 1, TimeOfDay(12, 0, 1));
8557         testTOD(TimeOfDay(12, 0, 0), 0, TimeOfDay(12, 0, 0));
8558         testTOD(TimeOfDay(12, 0, 0), -1, TimeOfDay(12, 0, 59));
8559
8560         testTOD(TimeOfDay(0, 0, 0), 1, TimeOfDay(0, 0, 1));
8561         testTOD(TimeOfDay(0, 0, 0), 0, TimeOfDay(0, 0, 0));
8562         testTOD(TimeOfDay(0, 0, 0), -1, TimeOfDay(0, 0, 59));
8563
8564         testTOD(TimeOfDay(23, 59, 59), 1, TimeOfDay(23, 59, 0));
8565         testTOD(TimeOfDay(23, 59, 59), 0, TimeOfDay(23, 59, 59));
8566         testTOD(TimeOfDay(23, 59, 59), -1, TimeOfDay(23, 59, 58));
8567
8568         auto tod = TimeOfDay(12, 27, 2);
8569         tod.roll!"seconds"(105).roll!"seconds"(-77);
8570         assert(tod == TimeOfDay(12, 27, 30));
8571
8572         const ctod = TimeOfDay(0, 0, 0);
8573         immutable itod = TimeOfDay(0, 0, 0);
8574         static assert(!__traits(compiles, ctod.roll!"seconds"(7)));
8575         static assert(!__traits(compiles, itod.roll!"seconds"(7)));
8576     }
8577
8578
8579     /++
8580         Gives the result of adding or subtracting a $(REF Duration, core,time)
8581         from this $(LREF TimeOfDay).
8582
8583         The legal types of arithmetic for $(LREF TimeOfDay) using this operator
8584         are
8585
8586         $(BOOKTABLE,
8587         $(TR $(TD TimeOfDay) $(TD +) $(TD Duration) $(TD -->) $(TD TimeOfDay))
8588         $(TR $(TD TimeOfDay) $(TD -) $(TD Duration) $(TD -->) $(TD TimeOfDay))
8589         )
8590
8591         Params:
8592             duration = The $(REF Duration, core,time) to add to or subtract from
8593                        this $(LREF TimeOfDay).
8594       +/
8595     TimeOfDay opBinary(string op)(Duration duration) const @safe pure nothrow @nogc
8596         if (op == "+" || op == "-")
8597     {
8598         TimeOfDay retval = this;
8599         immutable seconds = duration.total!"seconds";
8600         mixin("return retval._addSeconds(" ~ op ~ "seconds);");
8601     }
8602
8603     ///
8604     @safe unittest
8605     {
8606         import core.time : hours, minutes, seconds;
8607
8608         assert(TimeOfDay(12, 12, 12) + seconds(1) == TimeOfDay(12, 12, 13));
8609         assert(TimeOfDay(12, 12, 12) + minutes(1) == TimeOfDay(12, 13, 12));
8610         assert(TimeOfDay(12, 12, 12) + hours(1) == TimeOfDay(13, 12, 12));
8611         assert(TimeOfDay(23, 59, 59) + seconds(1) == TimeOfDay(0, 0, 0));
8612
8613         assert(TimeOfDay(12, 12, 12) - seconds(1) == TimeOfDay(12, 12, 11));
8614         assert(TimeOfDay(12, 12, 12) - minutes(1) == TimeOfDay(12, 11, 12));
8615         assert(TimeOfDay(12, 12, 12) - hours(1) == TimeOfDay(11, 12, 12));
8616         assert(TimeOfDay(0, 0, 0) - seconds(1) == TimeOfDay(23, 59, 59));
8617     }
8618
8619     @safe unittest
8620     {
8621         auto tod = TimeOfDay(12, 30, 33);
8622
8623         assert(tod + dur!"hours"(7) == TimeOfDay(19, 30, 33));
8624         assert(tod + dur!"hours"(-7) == TimeOfDay(5, 30, 33));
8625         assert(tod + dur!"minutes"(7) == TimeOfDay(12, 37, 33));
8626         assert(tod + dur!"minutes"(-7) == TimeOfDay(12, 23, 33));
8627         assert(tod + dur!"seconds"(7) == TimeOfDay(12, 30, 40));
8628         assert(tod + dur!"seconds"(-7) == TimeOfDay(12, 30, 26));
8629
8630         assert(tod + dur!"msecs"(7000) == TimeOfDay(12, 30, 40));
8631         assert(tod + dur!"msecs"(-7000) == TimeOfDay(12, 30, 26));
8632         assert(tod + dur!"usecs"(7_000_000) == TimeOfDay(12, 30, 40));
8633         assert(tod + dur!"usecs"(-7_000_000) == TimeOfDay(12, 30, 26));
8634         assert(tod + dur!"hnsecs"(70_000_000) == TimeOfDay(12, 30, 40));
8635         assert(tod + dur!"hnsecs"(-70_000_000) == TimeOfDay(12, 30, 26));
8636
8637         assert(tod - dur!"hours"(-7) == TimeOfDay(19, 30, 33));
8638         assert(tod - dur!"hours"(7) == TimeOfDay(5, 30, 33));
8639         assert(tod - dur!"minutes"(-7) == TimeOfDay(12, 37, 33));
8640         assert(tod - dur!"minutes"(7) == TimeOfDay(12, 23, 33));
8641         assert(tod - dur!"seconds"(-7) == TimeOfDay(12, 30, 40));
8642         assert(tod - dur!"seconds"(7) == TimeOfDay(12, 30, 26));
8643
8644         assert(tod - dur!"msecs"(-7000) == TimeOfDay(12, 30, 40));
8645         assert(tod - dur!"msecs"(7000) == TimeOfDay(12, 30, 26));
8646         assert(tod - dur!"usecs"(-7_000_000) == TimeOfDay(12, 30, 40));
8647         assert(tod - dur!"usecs"(7_000_000) == TimeOfDay(12, 30, 26));
8648         assert(tod - dur!"hnsecs"(-70_000_000) == TimeOfDay(12, 30, 40));
8649         assert(tod - dur!"hnsecs"(70_000_000) == TimeOfDay(12, 30, 26));
8650
8651         auto duration = dur!"hours"(11);
8652         const ctod = TimeOfDay(12, 30, 33);
8653         immutable itod = TimeOfDay(12, 30, 33);
8654         assert(tod + duration == TimeOfDay(23, 30, 33));
8655         assert(ctod + duration == TimeOfDay(23, 30, 33));
8656         assert(itod + duration == TimeOfDay(23, 30, 33));
8657
8658         assert(tod - duration == TimeOfDay(1, 30, 33));
8659         assert(ctod - duration == TimeOfDay(1, 30, 33));
8660         assert(itod - duration == TimeOfDay(1, 30, 33));
8661     }
8662
8663     // Explicitly undocumented. It will be removed in January 2018. @@@DEPRECATED_2018-01@@@
8664     deprecated("Use Duration instead of TickDuration.")
8665     TimeOfDay opBinary(string op)(TickDuration td) const @safe pure nothrow @nogc
8666         if (op == "+" || op == "-")
8667     {
8668         TimeOfDay retval = this;
8669         immutable seconds = td.seconds;
8670         mixin("return retval._addSeconds(" ~ op ~ "seconds);");
8671     }
8672
8673     deprecated @safe unittest
8674     {
8675         // This probably only runs in cases where gettimeofday() is used, but it's
8676         // hard to do this test correctly with variable ticksPerSec.
8677         if (TickDuration.ticksPerSec == 1_000_000)
8678         {
8679             auto tod = TimeOfDay(12, 30, 33);
8680
8681             assert(tod + TickDuration.from!"usecs"(7_000_000) == TimeOfDay(12, 30, 40));
8682             assert(tod + TickDuration.from!"usecs"(-7_000_000) == TimeOfDay(12, 30, 26));
8683
8684             assert(tod - TickDuration.from!"usecs"(-7_000_000) == TimeOfDay(12, 30, 40));
8685             assert(tod - TickDuration.from!"usecs"(7_000_000) == TimeOfDay(12, 30, 26));
8686         }
8687     }
8688
8689
8690     /++
8691         Gives the result of adding or subtracting a $(REF Duration, core,time)
8692         from this $(LREF TimeOfDay), as well as assigning the result to this
8693         $(LREF TimeOfDay).
8694
8695         The legal types of arithmetic for $(LREF TimeOfDay) using this operator
8696         are
8697
8698         $(BOOKTABLE,
8699         $(TR $(TD TimeOfDay) $(TD +) $(TD Duration) $(TD -->) $(TD TimeOfDay))
8700         $(TR $(TD TimeOfDay) $(TD -) $(TD Duration) $(TD -->) $(TD TimeOfDay))
8701         )
8702
8703         Params:
8704             duration = The $(REF Duration, core,time) to add to or subtract from
8705                        this $(LREF TimeOfDay).
8706       +/
8707     ref TimeOfDay opOpAssign(string op)(Duration duration) @safe pure nothrow @nogc
8708         if (op == "+" || op == "-")
8709     {
8710         immutable seconds = duration.total!"seconds";
8711         mixin("return _addSeconds(" ~ op ~ "seconds);");
8712     }
8713
8714     @safe unittest
8715     {
8716         auto duration = dur!"hours"(12);
8717
8718         assert(TimeOfDay(12, 30, 33) + dur!"hours"(7) == TimeOfDay(19, 30, 33));
8719         assert(TimeOfDay(12, 30, 33) + dur!"hours"(-7) == TimeOfDay(5, 30, 33));
8720         assert(TimeOfDay(12, 30, 33) + dur!"minutes"(7) == TimeOfDay(12, 37, 33));
8721         assert(TimeOfDay(12, 30, 33) + dur!"minutes"(-7) == TimeOfDay(12, 23, 33));
8722         assert(TimeOfDay(12, 30, 33) + dur!"seconds"(7) == TimeOfDay(12, 30, 40));
8723         assert(TimeOfDay(12, 30, 33) + dur!"seconds"(-7) == TimeOfDay(12, 30, 26));
8724
8725         assert(TimeOfDay(12, 30, 33) + dur!"msecs"(7000) == TimeOfDay(12, 30, 40));
8726         assert(TimeOfDay(12, 30, 33) + dur!"msecs"(-7000) == TimeOfDay(12, 30, 26));
8727         assert(TimeOfDay(12, 30, 33) + dur!"usecs"(7_000_000) == TimeOfDay(12, 30, 40));
8728         assert(TimeOfDay(12, 30, 33) + dur!"usecs"(-7_000_000) == TimeOfDay(12, 30, 26));
8729         assert(TimeOfDay(12, 30, 33) + dur!"hnsecs"(70_000_000) == TimeOfDay(12, 30, 40));
8730         assert(TimeOfDay(12, 30, 33) + dur!"hnsecs"(-70_000_000) == TimeOfDay(12, 30, 26));
8731
8732         assert(TimeOfDay(12, 30, 33) - dur!"hours"(-7) == TimeOfDay(19, 30, 33));
8733         assert(TimeOfDay(12, 30, 33) - dur!"hours"(7) == TimeOfDay(5, 30, 33));
8734         assert(TimeOfDay(12, 30, 33) - dur!"minutes"(-7) == TimeOfDay(12, 37, 33));
8735         assert(TimeOfDay(12, 30, 33) - dur!"minutes"(7) == TimeOfDay(12, 23, 33));
8736         assert(TimeOfDay(12, 30, 33) - dur!"seconds"(-7) == TimeOfDay(12, 30, 40));
8737         assert(TimeOfDay(12, 30, 33) - dur!"seconds"(7) == TimeOfDay(12, 30, 26));
8738
8739         assert(TimeOfDay(12, 30, 33) - dur!"msecs"(-7000) == TimeOfDay(12, 30, 40));
8740         assert(TimeOfDay(12, 30, 33) - dur!"msecs"(7000) == TimeOfDay(12, 30, 26));
8741         assert(TimeOfDay(12, 30, 33) - dur!"usecs"(-7_000_000) == TimeOfDay(12, 30, 40));
8742         assert(TimeOfDay(12, 30, 33) - dur!"usecs"(7_000_000) == TimeOfDay(12, 30, 26));
8743         assert(TimeOfDay(12, 30, 33) - dur!"hnsecs"(-70_000_000) == TimeOfDay(12, 30, 40));
8744         assert(TimeOfDay(12, 30, 33) - dur!"hnsecs"(70_000_000) == TimeOfDay(12, 30, 26));
8745
8746         auto tod = TimeOfDay(19, 17, 22);
8747         (tod += dur!"seconds"(9)) += dur!"seconds"(-7292);
8748         assert(tod == TimeOfDay(17, 15, 59));
8749
8750         const ctod = TimeOfDay(12, 33, 30);
8751         immutable itod = TimeOfDay(12, 33, 30);
8752         static assert(!__traits(compiles, ctod += duration));
8753         static assert(!__traits(compiles, itod += duration));
8754         static assert(!__traits(compiles, ctod -= duration));
8755         static assert(!__traits(compiles, itod -= duration));
8756     }
8757
8758     // Explicitly undocumented. It will be removed in January 2018. @@@DEPRECATED_2018-01@@@
8759     deprecated("Use Duration instead of TickDuration.")
8760     ref TimeOfDay opOpAssign(string op)(TickDuration td) @safe pure nothrow @nogc
8761         if (op == "+" || op == "-")
8762     {
8763         immutable seconds = td.seconds;
8764         mixin("return _addSeconds(" ~ op ~ "seconds);");
8765     }
8766
8767     deprecated @safe unittest
8768     {
8769         // This probably only runs in cases where gettimeofday() is used, but it's
8770         // hard to do this test correctly with variable ticksPerSec.
8771         if (TickDuration.ticksPerSec == 1_000_000)
8772         {
8773             {
8774                 auto tod = TimeOfDay(12, 30, 33);
8775                 tod += TickDuration.from!"usecs"(7_000_000);
8776                 assert(tod == TimeOfDay(12, 30, 40));
8777             }
8778
8779             {
8780                 auto tod = TimeOfDay(12, 30, 33);
8781                 tod += TickDuration.from!"usecs"(-7_000_000);
8782                 assert(tod == TimeOfDay(12, 30, 26));
8783             }
8784
8785             {
8786                 auto tod = TimeOfDay(12, 30, 33);
8787                 tod -= TickDuration.from!"usecs"(-7_000_000);
8788                 assert(tod == TimeOfDay(12, 30, 40));
8789             }
8790
8791             {
8792                 auto tod = TimeOfDay(12, 30, 33);
8793                 tod -= TickDuration.from!"usecs"(7_000_000);
8794                 assert(tod == TimeOfDay(12, 30, 26));
8795             }
8796         }
8797     }
8798
8799
8800     /++
8801         Gives the difference between two $(LREF TimeOfDay)s.
8802
8803         The legal types of arithmetic for $(LREF TimeOfDay) using this operator
8804         are
8805
8806         $(BOOKTABLE,
8807         $(TR $(TD TimeOfDay) $(TD -) $(TD TimeOfDay) $(TD -->) $(TD duration))
8808         )
8809
8810         Params:
8811             rhs = The $(LREF TimeOfDay) to subtract from this one.
8812       +/
8813     Duration opBinary(string op)(in TimeOfDay rhs) const @safe pure nothrow @nogc
8814         if (op == "-")
8815     {
8816         immutable lhsSec = _hour * 3600 + _minute * 60 + _second;
8817         immutable rhsSec = rhs._hour * 3600 + rhs._minute * 60 + rhs._second;
8818
8819         return dur!"seconds"(lhsSec - rhsSec);
8820     }
8821
8822     @safe unittest
8823     {
8824         auto tod = TimeOfDay(12, 30, 33);
8825
8826         assert(TimeOfDay(7, 12, 52) - TimeOfDay(12, 30, 33) == dur!"seconds"(-19_061));
8827         assert(TimeOfDay(12, 30, 33) - TimeOfDay(7, 12, 52) == dur!"seconds"(19_061));
8828         assert(TimeOfDay(12, 30, 33) - TimeOfDay(14, 30, 33) == dur!"seconds"(-7200));
8829         assert(TimeOfDay(14, 30, 33) - TimeOfDay(12, 30, 33) == dur!"seconds"(7200));
8830         assert(TimeOfDay(12, 30, 33) - TimeOfDay(12, 34, 33) == dur!"seconds"(-240));
8831         assert(TimeOfDay(12, 34, 33) - TimeOfDay(12, 30, 33) == dur!"seconds"(240));
8832         assert(TimeOfDay(12, 30, 33) - TimeOfDay(12, 30, 34) == dur!"seconds"(-1));
8833         assert(TimeOfDay(12, 30, 34) - TimeOfDay(12, 30, 33) == dur!"seconds"(1));
8834
8835         const ctod = TimeOfDay(12, 30, 33);
8836         immutable itod = TimeOfDay(12, 30, 33);
8837         assert(tod - tod == Duration.zero);
8838         assert(ctod - tod == Duration.zero);
8839         assert(itod - tod == Duration.zero);
8840
8841         assert(tod - ctod == Duration.zero);
8842         assert(ctod - ctod == Duration.zero);
8843         assert(itod - ctod == Duration.zero);
8844
8845         assert(tod - itod == Duration.zero);
8846         assert(ctod - itod == Duration.zero);
8847         assert(itod - itod == Duration.zero);
8848     }
8849
8850
8851     /++
8852         Converts this $(LREF TimeOfDay) to a string with the format HHMMSS.
8853       +/
8854     string toISOString() const @safe pure nothrow
8855     {
8856         import std.format : format;
8857         try
8858             return format("%02d%02d%02d", _hour, _minute, _second);
8859         catch (Exception e)
8860             assert(0, "format() threw.");
8861     }
8862
8863     ///
8864     @safe unittest
8865     {
8866         assert(TimeOfDay(0, 0, 0).toISOString() == "000000");
8867         assert(TimeOfDay(12, 30, 33).toISOString() == "123033");
8868     }
8869
8870     @safe unittest
8871     {
8872         auto tod = TimeOfDay(12, 30, 33);
8873         const ctod = TimeOfDay(12, 30, 33);
8874         immutable itod = TimeOfDay(12, 30, 33);
8875         assert(tod.toISOString() == "123033");
8876         assert(ctod.toISOString() == "123033");
8877         assert(itod.toISOString() == "123033");
8878     }
8879
8880
8881     /++
8882         Converts this $(LREF TimeOfDay) to a string with the format HH:MM:SS.
8883       +/
8884     string toISOExtString() const @safe pure nothrow
8885     {
8886         import std.format : format;
8887         try
8888             return format("%02d:%02d:%02d", _hour, _minute, _second);
8889         catch (Exception e)
8890             assert(0, "format() threw.");
8891     }
8892
8893     ///
8894     @safe unittest
8895     {
8896         assert(TimeOfDay(0, 0, 0).toISOExtString() == "00:00:00");
8897         assert(TimeOfDay(12, 30, 33).toISOExtString() == "12:30:33");
8898     }
8899
8900     @safe unittest
8901     {
8902         auto tod = TimeOfDay(12, 30, 33);
8903         const ctod = TimeOfDay(12, 30, 33);
8904         immutable itod = TimeOfDay(12, 30, 33);
8905         assert(tod.toISOExtString() == "12:30:33");
8906         assert(ctod.toISOExtString() == "12:30:33");
8907         assert(itod.toISOExtString() == "12:30:33");
8908     }
8909
8910
8911     /++
8912         Converts this TimeOfDay to a string.
8913
8914         This function exists to make it easy to convert a $(LREF TimeOfDay) to a
8915         string for code that does not care what the exact format is - just that
8916         it presents the information in a clear manner. It also makes it easy to
8917         simply convert a $(LREF TimeOfDay) to a string when using functions such
8918         as `to!string`, `format`, or `writeln` which use toString to convert
8919         user-defined types. So, it is unlikely that much code will call
8920         toString directly.
8921
8922         The format of the string is purposefully unspecified, and code that
8923         cares about the format of the string should use `toISOString`,
8924         `toISOExtString`, or some other custom formatting function that
8925         explicitly generates the format that the code needs. The reason is that
8926         the code is then clear about what format it's using, making it less
8927         error-prone to maintain the code and interact with other software that
8928         consumes the generated strings. It's for this same reason that
8929         $(LREF TimeOfDay) has no `fromString` function, whereas it does have
8930         `fromISOString` and `fromISOExtString`.
8931
8932         The format returned by toString may or may not change in the future.
8933       +/
8934     string toString() const @safe pure nothrow
8935     {
8936         return toISOExtString();
8937     }
8938
8939     @safe unittest
8940     {
8941         auto tod = TimeOfDay(12, 30, 33);
8942         const ctod = TimeOfDay(12, 30, 33);
8943         immutable itod = TimeOfDay(12, 30, 33);
8944         assert(tod.toString());
8945         assert(ctod.toString());
8946         assert(itod.toString());
8947     }
8948
8949
8950     /++
8951         Creates a $(LREF TimeOfDay) from a string with the format HHMMSS.
8952         Whitespace is stripped from the given string.
8953
8954         Params:
8955             isoString = A string formatted in the ISO format for times.
8956
8957         Throws:
8958             $(REF DateTimeException,std,datetime,date) if the given string is
8959             not in the ISO format or if the resulting $(LREF TimeOfDay) would
8960             not be valid.
8961       +/
8962     static TimeOfDay fromISOString(S)(in S isoString) @safe pure
8963         if (isSomeString!S)
8964     {
8965         import std.conv : to, text, ConvException;
8966         import std.exception : enforce;
8967         import std.string : strip;
8968
8969         int hours, minutes, seconds;
8970         auto str = strip(isoString);
8971
8972         enforce!DateTimeException(str.length == 6, text("Invalid ISO String: ", isoString));
8973
8974         try
8975         {
8976             // cast to int from uint is used because it checks for
8977             // non digits without extra loops
8978             hours = cast(int) to!uint(str[0 .. 2]);
8979             minutes = cast(int) to!uint(str[2 .. 4]);
8980             seconds = cast(int) to!uint(str[4 .. $]);
8981         }
8982         catch (ConvException)
8983         {
8984             throw new DateTimeException(text("Invalid ISO String: ", isoString));
8985         }
8986
8987         return TimeOfDay(hours, minutes, seconds);
8988     }
8989
8990     ///
8991     @safe unittest
8992     {
8993         assert(TimeOfDay.fromISOString("000000") == TimeOfDay(0, 0, 0));
8994         assert(TimeOfDay.fromISOString("123033") == TimeOfDay(12, 30, 33));
8995         assert(TimeOfDay.fromISOString(" 123033 ") == TimeOfDay(12, 30, 33));
8996     }
8997
8998     @safe unittest
8999     {
9000         assertThrown!DateTimeException(TimeOfDay.fromISOString(""));
9001         assertThrown!DateTimeException(TimeOfDay.fromISOString("0"));
9002         assertThrown!DateTimeException(TimeOfDay.fromISOString("00"));
9003         assertThrown!DateTimeException(TimeOfDay.fromISOString("000"));
9004         assertThrown!DateTimeException(TimeOfDay.fromISOString("0000"));
9005         assertThrown!DateTimeException(TimeOfDay.fromISOString("00000"));
9006         assertThrown!DateTimeException(TimeOfDay.fromISOString("13033"));
9007         assertThrown!DateTimeException(TimeOfDay.fromISOString("1277"));
9008         assertThrown!DateTimeException(TimeOfDay.fromISOString("12707"));
9009         assertThrown!DateTimeException(TimeOfDay.fromISOString("12070"));
9010         assertThrown!DateTimeException(TimeOfDay.fromISOString("12303a"));
9011         assertThrown!DateTimeException(TimeOfDay.fromISOString("1230a3"));
9012         assertThrown!DateTimeException(TimeOfDay.fromISOString("123a33"));
9013         assertThrown!DateTimeException(TimeOfDay.fromISOString("12a033"));
9014         assertThrown!DateTimeException(TimeOfDay.fromISOString("1a0033"));
9015         assertThrown!DateTimeException(TimeOfDay.fromISOString("a20033"));
9016         assertThrown!DateTimeException(TimeOfDay.fromISOString("1200330"));
9017         assertThrown!DateTimeException(TimeOfDay.fromISOString("0120033"));
9018         assertThrown!DateTimeException(TimeOfDay.fromISOString("-120033"));
9019         assertThrown!DateTimeException(TimeOfDay.fromISOString("+120033"));
9020         assertThrown!DateTimeException(TimeOfDay.fromISOString("120033am"));
9021         assertThrown!DateTimeException(TimeOfDay.fromISOString("120033pm"));
9022
9023         assertThrown!DateTimeException(TimeOfDay.fromISOString("0::"));
9024         assertThrown!DateTimeException(TimeOfDay.fromISOString(":0:"));
9025         assertThrown!DateTimeException(TimeOfDay.fromISOString("::0"));
9026         assertThrown!DateTimeException(TimeOfDay.fromISOString("0:0:0"));
9027         assertThrown!DateTimeException(TimeOfDay.fromISOString("0:0:00"));
9028         assertThrown!DateTimeException(TimeOfDay.fromISOString("0:00:0"));
9029         assertThrown!DateTimeException(TimeOfDay.fromISOString("00:0:0"));
9030         assertThrown!DateTimeException(TimeOfDay.fromISOString("00:00:0"));
9031         assertThrown!DateTimeException(TimeOfDay.fromISOString("00:0:00"));
9032         assertThrown!DateTimeException(TimeOfDay.fromISOString("13:0:33"));
9033         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:7:7"));
9034         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:7:07"));
9035         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:07:0"));
9036         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:30:3a"));
9037         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:30:a3"));
9038         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:3a:33"));
9039         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:a0:33"));
9040         assertThrown!DateTimeException(TimeOfDay.fromISOString("1a:00:33"));
9041         assertThrown!DateTimeException(TimeOfDay.fromISOString("a2:00:33"));
9042         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:003:30"));
9043         assertThrown!DateTimeException(TimeOfDay.fromISOString("120:03:30"));
9044         assertThrown!DateTimeException(TimeOfDay.fromISOString("012:00:33"));
9045         assertThrown!DateTimeException(TimeOfDay.fromISOString("01:200:33"));
9046         assertThrown!DateTimeException(TimeOfDay.fromISOString("-12:00:33"));
9047         assertThrown!DateTimeException(TimeOfDay.fromISOString("+12:00:33"));
9048         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:00:33am"));
9049         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:00:33pm"));
9050
9051         assertThrown!DateTimeException(TimeOfDay.fromISOString("12:00:33"));
9052
9053         assert(TimeOfDay.fromISOString("011217") == TimeOfDay(1, 12, 17));
9054         assert(TimeOfDay.fromISOString("001412") == TimeOfDay(0, 14, 12));
9055         assert(TimeOfDay.fromISOString("000007") == TimeOfDay(0, 0, 7));
9056         assert(TimeOfDay.fromISOString("011217 ") == TimeOfDay(1, 12, 17));
9057         assert(TimeOfDay.fromISOString(" 011217") == TimeOfDay(1, 12, 17));
9058         assert(TimeOfDay.fromISOString(" 011217 ") == TimeOfDay(1, 12, 17));
9059     }
9060
9061     // bug# 17801
9062     @safe unittest
9063     {
9064         import std.conv : to;
9065         import std.meta : AliasSeq;
9066         foreach (C; AliasSeq!(char, wchar, dchar))
9067         {
9068             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
9069                 assert(TimeOfDay.fromISOString(to!S("141516")) == TimeOfDay(14, 15, 16));
9070         }
9071     }
9072
9073
9074     /++
9075         Creates a $(LREF TimeOfDay) from a string with the format HH:MM:SS.
9076         Whitespace is stripped from the given string.
9077
9078         Params:
9079             isoExtString = A string formatted in the ISO Extended format for
9080             times.
9081
9082         Throws:
9083             $(REF DateTimeException,std,datetime,date) if the given string is
9084             not in the ISO Extended format or if the resulting $(LREF TimeOfDay)
9085             would not be valid.
9086       +/
9087     static TimeOfDay fromISOExtString(S)(in S isoExtString) @safe pure
9088         if (isSomeString!S)
9089     {
9090         import std.algorithm.searching : all;
9091         import std.ascii : isDigit;
9092         import std.conv : to;
9093         import std.exception : enforce;
9094         import std.format : format;
9095         import std.string : strip;
9096
9097         auto dstr = to!dstring(strip(isoExtString));
9098
9099         enforce(dstr.length == 8, new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
9100
9101         auto hours = dstr[0 .. 2];
9102         auto minutes = dstr[3 .. 5];
9103         auto seconds = dstr[6 .. $];
9104
9105         enforce(dstr[2] == ':', new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
9106         enforce(dstr[5] == ':', new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
9107         enforce(all!isDigit(hours),
9108                 new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
9109         enforce(all!isDigit(minutes),
9110                 new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
9111         enforce(all!isDigit(seconds),
9112                 new DateTimeException(format("Invalid ISO Extended String: %s", isoExtString)));
9113
9114         return TimeOfDay(to!int(hours), to!int(minutes), to!int(seconds));
9115     }
9116
9117     ///
9118     @safe unittest
9119     {
9120         assert(TimeOfDay.fromISOExtString("00:00:00") == TimeOfDay(0, 0, 0));
9121         assert(TimeOfDay.fromISOExtString("12:30:33") == TimeOfDay(12, 30, 33));
9122         assert(TimeOfDay.fromISOExtString(" 12:30:33 ") == TimeOfDay(12, 30, 33));
9123     }
9124
9125     @safe unittest
9126     {
9127         assertThrown!DateTimeException(TimeOfDay.fromISOExtString(""));
9128         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("0"));
9129         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("00"));
9130         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("000"));
9131         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("0000"));
9132         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("00000"));
9133         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("13033"));
9134         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("1277"));
9135         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12707"));
9136         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12070"));
9137         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12303a"));
9138         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("1230a3"));
9139         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("123a33"));
9140         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12a033"));
9141         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("1a0033"));
9142         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("a20033"));
9143         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("1200330"));
9144         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("0120033"));
9145         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("-120033"));
9146         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("+120033"));
9147         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("120033am"));
9148         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("120033pm"));
9149
9150         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("0::"));
9151         assertThrown!DateTimeException(TimeOfDay.fromISOExtString(":0:"));
9152         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("::0"));
9153         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("0:0:0"));
9154         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("0:0:00"));
9155         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("0:00:0"));
9156         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("00:0:0"));
9157         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("00:00:0"));
9158         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("00:0:00"));
9159         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("13:0:33"));
9160         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:7:7"));
9161         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:7:07"));
9162         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:07:0"));
9163         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:30:3a"));
9164         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:30:a3"));
9165         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:3a:33"));
9166         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:a0:33"));
9167         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("1a:00:33"));
9168         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("a2:00:33"));
9169         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:003:30"));
9170         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("120:03:30"));
9171         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("012:00:33"));
9172         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("01:200:33"));
9173         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("-12:00:33"));
9174         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("+12:00:33"));
9175         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:00:33am"));
9176         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("12:00:33pm"));
9177
9178         assertThrown!DateTimeException(TimeOfDay.fromISOExtString("120033"));
9179
9180         assert(TimeOfDay.fromISOExtString("01:12:17") == TimeOfDay(1, 12, 17));
9181         assert(TimeOfDay.fromISOExtString("00:14:12") == TimeOfDay(0, 14, 12));
9182         assert(TimeOfDay.fromISOExtString("00:00:07") == TimeOfDay(0, 0, 7));
9183         assert(TimeOfDay.fromISOExtString("01:12:17 ") == TimeOfDay(1, 12, 17));
9184         assert(TimeOfDay.fromISOExtString(" 01:12:17") == TimeOfDay(1, 12, 17));
9185         assert(TimeOfDay.fromISOExtString(" 01:12:17 ") == TimeOfDay(1, 12, 17));
9186     }
9187
9188     // bug# 17801
9189     @safe unittest
9190     {
9191         import std.conv : to;
9192         import std.meta : AliasSeq;
9193         foreach (C; AliasSeq!(char, wchar, dchar))
9194         {
9195             foreach (S; AliasSeq!(C[], const(C)[], immutable(C)[]))
9196                 assert(TimeOfDay.fromISOExtString(to!S("14:15:16")) == TimeOfDay(14, 15, 16));
9197         }
9198     }
9199
9200
9201     /++
9202         Returns midnight.
9203       +/
9204     @property static TimeOfDay min() @safe pure nothrow @nogc
9205     {
9206         return TimeOfDay.init;
9207     }
9208
9209     @safe unittest
9210     {
9211         assert(TimeOfDay.min.hour == 0);
9212         assert(TimeOfDay.min.minute == 0);
9213         assert(TimeOfDay.min.second == 0);
9214         assert(TimeOfDay.min < TimeOfDay.max);
9215     }
9216
9217
9218     /++
9219         Returns one second short of midnight.
9220       +/
9221     @property static TimeOfDay max() @safe pure nothrow @nogc
9222     {
9223         auto tod = TimeOfDay.init;
9224         tod._hour = maxHour;
9225         tod._minute = maxMinute;
9226         tod._second = maxSecond;
9227
9228         return tod;
9229     }
9230
9231     @safe unittest
9232     {
9233         assert(TimeOfDay.max.hour == 23);
9234         assert(TimeOfDay.max.minute == 59);
9235         assert(TimeOfDay.max.second == 59);
9236         assert(TimeOfDay.max > TimeOfDay.min);
9237     }
9238
9239
9240 private:
9241
9242     /+
9243         Add seconds to the time of day. Negative values will subtract. If the
9244         number of seconds overflows (or underflows), then the seconds will wrap,
9245         increasing (or decreasing) the number of minutes accordingly. If the
9246         number of minutes overflows (or underflows), then the minutes will wrap.
9247         If the number of minutes overflows(or underflows), then the hour will
9248         wrap. (e.g. adding 90 seconds to 23:59:00 would result in 00:00:30).
9249
9250         Params:
9251             seconds = The number of seconds to add to this TimeOfDay.
9252       +/
9253     ref TimeOfDay _addSeconds(long seconds) return @safe pure nothrow @nogc
9254     {
9255         long hnsecs = convert!("seconds", "hnsecs")(seconds);
9256         hnsecs += convert!("hours", "hnsecs")(_hour);
9257         hnsecs += convert!("minutes", "hnsecs")(_minute);
9258         hnsecs += convert!("seconds", "hnsecs")(_second);
9259
9260         hnsecs %= convert!("days", "hnsecs")(1);
9261
9262         if (hnsecs < 0)
9263             hnsecs += convert!("days", "hnsecs")(1);
9264
9265         immutable newHours = splitUnitsFromHNSecs!"hours"(hnsecs);
9266         immutable newMinutes = splitUnitsFromHNSecs!"minutes"(hnsecs);
9267         immutable newSeconds = splitUnitsFromHNSecs!"seconds"(hnsecs);
9268
9269         _hour = cast(ubyte) newHours;
9270         _minute = cast(ubyte) newMinutes;
9271         _second = cast(ubyte) newSeconds;
9272
9273         return this;
9274     }
9275
9276     @safe unittest
9277     {
9278         static void testTOD(TimeOfDay orig, int seconds, in TimeOfDay expected, size_t line = __LINE__)
9279         {
9280             orig._addSeconds(seconds);
9281             assert(orig == expected);
9282         }
9283
9284         testTOD(TimeOfDay(12, 30, 33), 0, TimeOfDay(12, 30, 33));
9285         testTOD(TimeOfDay(12, 30, 33), 1, TimeOfDay(12, 30, 34));
9286         testTOD(TimeOfDay(12, 30, 33), 2, TimeOfDay(12, 30, 35));
9287         testTOD(TimeOfDay(12, 30, 33), 3, TimeOfDay(12, 30, 36));
9288         testTOD(TimeOfDay(12, 30, 33), 4, TimeOfDay(12, 30, 37));
9289         testTOD(TimeOfDay(12, 30, 33), 5, TimeOfDay(12, 30, 38));
9290         testTOD(TimeOfDay(12, 30, 33), 10, TimeOfDay(12, 30, 43));
9291         testTOD(TimeOfDay(12, 30, 33), 15, TimeOfDay(12, 30, 48));
9292         testTOD(TimeOfDay(12, 30, 33), 26, TimeOfDay(12, 30, 59));
9293         testTOD(TimeOfDay(12, 30, 33), 27, TimeOfDay(12, 31, 0));
9294         testTOD(TimeOfDay(12, 30, 33), 30, TimeOfDay(12, 31, 3));
9295         testTOD(TimeOfDay(12, 30, 33), 59, TimeOfDay(12, 31, 32));
9296         testTOD(TimeOfDay(12, 30, 33), 60, TimeOfDay(12, 31, 33));
9297         testTOD(TimeOfDay(12, 30, 33), 61, TimeOfDay(12, 31, 34));
9298
9299         testTOD(TimeOfDay(12, 30, 33), 1766, TimeOfDay(12, 59, 59));
9300         testTOD(TimeOfDay(12, 30, 33), 1767, TimeOfDay(13, 0, 0));
9301         testTOD(TimeOfDay(12, 30, 33), 1768, TimeOfDay(13, 0, 1));
9302         testTOD(TimeOfDay(12, 30, 33), 2007, TimeOfDay(13, 4, 0));
9303         testTOD(TimeOfDay(12, 30, 33), 3599, TimeOfDay(13, 30, 32));
9304         testTOD(TimeOfDay(12, 30, 33), 3600, TimeOfDay(13, 30, 33));
9305         testTOD(TimeOfDay(12, 30, 33), 3601, TimeOfDay(13, 30, 34));
9306         testTOD(TimeOfDay(12, 30, 33), 7200, TimeOfDay(14, 30, 33));
9307
9308         testTOD(TimeOfDay(12, 30, 33), -1, TimeOfDay(12, 30, 32));
9309         testTOD(TimeOfDay(12, 30, 33), -2, TimeOfDay(12, 30, 31));
9310         testTOD(TimeOfDay(12, 30, 33), -3, TimeOfDay(12, 30, 30));
9311         testTOD(TimeOfDay(12, 30, 33), -4, TimeOfDay(12, 30, 29));
9312         testTOD(TimeOfDay(12, 30, 33), -5, TimeOfDay(12, 30, 28));
9313         testTOD(TimeOfDay(12, 30, 33), -10, TimeOfDay(12, 30, 23));
9314         testTOD(TimeOfDay(12, 30, 33), -15, TimeOfDay(12, 30, 18));
9315         testTOD(TimeOfDay(12, 30, 33), -33, TimeOfDay(12, 30, 0));
9316         testTOD(TimeOfDay(12, 30, 33), -34, TimeOfDay(12, 29, 59));
9317         testTOD(TimeOfDay(12, 30, 33), -35, TimeOfDay(12, 29, 58));
9318         testTOD(TimeOfDay(12, 30, 33), -59, TimeOfDay(12, 29, 34));
9319         testTOD(TimeOfDay(12, 30, 33), -60, TimeOfDay(12, 29, 33));
9320         testTOD(TimeOfDay(12, 30, 33), -61, TimeOfDay(12, 29, 32));
9321
9322         testTOD(TimeOfDay(12, 30, 33), -1833, TimeOfDay(12, 0, 0));
9323         testTOD(TimeOfDay(12, 30, 33), -1834, TimeOfDay(11, 59, 59));
9324         testTOD(TimeOfDay(12, 30, 33), -3600, TimeOfDay(11, 30, 33));
9325         testTOD(TimeOfDay(12, 30, 33), -3601, TimeOfDay(11, 30, 32));
9326         testTOD(TimeOfDay(12, 30, 33), -5134, TimeOfDay(11, 4, 59));
9327         testTOD(TimeOfDay(12, 30, 33), -7200, TimeOfDay(10, 30, 33));
9328
9329         testTOD(TimeOfDay(12, 30, 0), 1, TimeOfDay(12, 30, 1));
9330         testTOD(TimeOfDay(12, 30, 0), 0, TimeOfDay(12, 30, 0));
9331         testTOD(TimeOfDay(12, 30, 0), -1, TimeOfDay(12, 29, 59));
9332
9333         testTOD(TimeOfDay(12, 0, 0), 1, TimeOfDay(12, 0, 1));
9334         testTOD(TimeOfDay(12, 0, 0), 0, TimeOfDay(12, 0, 0));
9335         testTOD(TimeOfDay(12, 0, 0), -1, TimeOfDay(11, 59, 59));
9336
9337         testTOD(TimeOfDay(0, 0, 0), 1, TimeOfDay(0, 0, 1));
9338         testTOD(TimeOfDay(0, 0, 0), 0, TimeOfDay(0, 0, 0));
9339         testTOD(TimeOfDay(0, 0, 0), -1, TimeOfDay(23, 59, 59));
9340
9341         testTOD(TimeOfDay(23, 59, 59), 1, TimeOfDay(0, 0, 0));
9342         testTOD(TimeOfDay(23, 59, 59), 0, TimeOfDay(23, 59, 59));
9343         testTOD(TimeOfDay(23, 59, 59), -1, TimeOfDay(23, 59, 58));
9344
9345         const ctod = TimeOfDay(0, 0, 0);
9346         immutable itod = TimeOfDay(0, 0, 0);
9347         static assert(!__traits(compiles, ctod._addSeconds(7)));
9348         static assert(!__traits(compiles, itod._addSeconds(7)));
9349     }
9350
9351
9352     /+
9353         Whether the given values form a valid $(LREF TimeOfDay).
9354      +/
9355     static bool _valid(int hour, int minute, int second) @safe pure nothrow @nogc
9356     {
9357         return valid!"hours"(hour) && valid!"minutes"(minute) && valid!"seconds"(second);
9358     }
9359
9360
9361     @safe pure invariant()
9362     {
9363         import std.format : format;
9364         assert(_valid(_hour, _minute, _second),
9365                format("Invariant Failure: hour [%s] minute [%s] second [%s]", _hour, _minute, _second));
9366     }
9367
9368
9369 package:
9370
9371     ubyte _hour;
9372     ubyte _minute;
9373     ubyte _second;
9374
9375     enum ubyte maxHour   = 24 - 1;
9376     enum ubyte maxMinute = 60 - 1;
9377     enum ubyte maxSecond = 60 - 1;
9378 }
9379
9380
9381 /++
9382     Returns whether the given value is valid for the given unit type when in a
9383     time point. Naturally, a duration is not held to a particular range, but
9384     the values in a time point are (e.g. a month must be in the range of
9385     1 - 12 inclusive).
9386
9387     Params:
9388         units = The units of time to validate.
9389         value = The number to validate.
9390   +/
9391 bool valid(string units)(int value) @safe pure nothrow @nogc
9392 if (units == "months" ||
9393     units == "hours" ||
9394     units == "minutes" ||
9395     units == "seconds")
9396 {
9397     static if (units == "months")
9398         return value >= Month.jan && value <= Month.dec;
9399     else static if (units == "hours")
9400         return value >= 0 && value <= 23;
9401     else static if (units == "minutes")
9402         return value >= 0 && value <= 59;
9403     else static if (units == "seconds")
9404         return value >= 0 && value <= 59;
9405 }
9406
9407 ///
9408 @safe unittest
9409 {
9410     assert(valid!"hours"(12));
9411     assert(!valid!"hours"(32));
9412     assert(valid!"months"(12));
9413     assert(!valid!"months"(13));
9414 }
9415
9416 /++
9417     Returns whether the given day is valid for the given year and month.
9418
9419     Params:
9420         units = The units of time to validate.
9421         year  = The year of the day to validate.
9422         month = The month of the day to validate (January is 1).
9423         day   = The day to validate.
9424   +/
9425 bool valid(string units)(int year, int month, int day) @safe pure nothrow @nogc
9426 if (units == "days")
9427 {
9428     return day > 0 && day <= maxDay(year, month);
9429 }
9430
9431 ///
9432 @safe pure nothrow @nogc unittest
9433 {
9434     assert(valid!"days"(2016, 2, 29));
9435     assert(!valid!"days"(2016, 2, 30));
9436     assert(valid!"days"(2017, 2, 20));
9437     assert(!valid!"days"(2017, 2, 29));
9438 }
9439
9440
9441 /++
9442     Params:
9443         units = The units of time to validate.
9444         value = The number to validate.
9445         file  = The file that the $(LREF DateTimeException) will list if thrown.
9446         line  = The line number that the $(LREF DateTimeException) will list if
9447                 thrown.
9448
9449     Throws:
9450         $(LREF DateTimeException) if $(D valid!units(value)) is false.
9451   +/
9452 void enforceValid(string units)(int value, string file = __FILE__, size_t line = __LINE__) @safe pure
9453 if (units == "months" ||
9454     units == "hours" ||
9455     units == "minutes" ||
9456     units == "seconds")
9457 {
9458     import std.format : format;
9459
9460     static if (units == "months")
9461     {
9462         if (!valid!units(value))
9463             throw new DateTimeException(format("%s is not a valid month of the year.", value), file, line);
9464     }
9465     else static if (units == "hours")
9466     {
9467         if (!valid!units(value))
9468             throw new DateTimeException(format("%s is not a valid hour of the day.", value), file, line);
9469     }
9470     else static if (units == "minutes")
9471     {
9472         if (!valid!units(value))
9473             throw new DateTimeException(format("%s is not a valid minute of an hour.", value), file, line);
9474     }
9475     else static if (units == "seconds")
9476     {
9477         if (!valid!units(value))
9478             throw new DateTimeException(format("%s is not a valid second of a minute.", value), file, line);
9479     }
9480 }
9481
9482
9483 /++
9484     Params:
9485         units = The units of time to validate.
9486         year  = The year of the day to validate.
9487         month = The month of the day to validate.
9488         day   = The day to validate.
9489         file  = The file that the $(LREF DateTimeException) will list if thrown.
9490         line  = The line number that the $(LREF DateTimeException) will list if
9491                 thrown.
9492
9493     Throws:
9494         $(LREF DateTimeException) if $(D valid!"days"(year, month, day)) is false.
9495   +/
9496 void enforceValid(string units)
9497                  (int year, Month month, int day, string file = __FILE__, size_t line = __LINE__) @safe pure
9498 if (units == "days")
9499 {
9500     import std.format : format;
9501     if (!valid!"days"(year, month, day))
9502         throw new DateTimeException(format("%s is not a valid day in %s in %s", day, month, year), file, line);
9503 }
9504
9505
9506 /++
9507     Returns the number of days from the current day of the week to the given
9508     day of the week. If they are the same, then the result is 0.
9509
9510     Params:
9511         currDoW = The current day of the week.
9512         dow     = The day of the week to get the number of days to.
9513   +/
9514 int daysToDayOfWeek(DayOfWeek currDoW, DayOfWeek dow) @safe pure nothrow @nogc
9515 {
9516     if (currDoW == dow)
9517         return 0;
9518     if (currDoW < dow)
9519         return dow - currDoW;
9520     return DayOfWeek.sat - currDoW + dow + 1;
9521 }
9522
9523 ///
9524 @safe pure nothrow @nogc unittest
9525 {
9526     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.mon) == 0);
9527     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.sun) == 6);
9528     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.wed) == 2);
9529 }
9530
9531 @safe unittest
9532 {
9533     assert(daysToDayOfWeek(DayOfWeek.sun, DayOfWeek.sun) == 0);
9534     assert(daysToDayOfWeek(DayOfWeek.sun, DayOfWeek.mon) == 1);
9535     assert(daysToDayOfWeek(DayOfWeek.sun, DayOfWeek.tue) == 2);
9536     assert(daysToDayOfWeek(DayOfWeek.sun, DayOfWeek.wed) == 3);
9537     assert(daysToDayOfWeek(DayOfWeek.sun, DayOfWeek.thu) == 4);
9538     assert(daysToDayOfWeek(DayOfWeek.sun, DayOfWeek.fri) == 5);
9539     assert(daysToDayOfWeek(DayOfWeek.sun, DayOfWeek.sat) == 6);
9540
9541     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.sun) == 6);
9542     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.mon) == 0);
9543     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.tue) == 1);
9544     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.wed) == 2);
9545     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.thu) == 3);
9546     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.fri) == 4);
9547     assert(daysToDayOfWeek(DayOfWeek.mon, DayOfWeek.sat) == 5);
9548
9549     assert(daysToDayOfWeek(DayOfWeek.tue, DayOfWeek.sun) == 5);
9550     assert(daysToDayOfWeek(DayOfWeek.tue, DayOfWeek.mon) == 6);
9551     assert(daysToDayOfWeek(DayOfWeek.tue, DayOfWeek.tue) == 0);
9552     assert(daysToDayOfWeek(DayOfWeek.tue, DayOfWeek.wed) == 1);
9553     assert(daysToDayOfWeek(DayOfWeek.tue, DayOfWeek.thu) == 2);
9554     assert(daysToDayOfWeek(DayOfWeek.tue, DayOfWeek.fri) == 3);
9555     assert(daysToDayOfWeek(DayOfWeek.tue, DayOfWeek.sat) == 4);
9556
9557     assert(daysToDayOfWeek(DayOfWeek.wed, DayOfWeek.sun) == 4);
9558     assert(daysToDayOfWeek(DayOfWeek.wed, DayOfWeek.mon) == 5);
9559     assert(daysToDayOfWeek(DayOfWeek.wed, DayOfWeek.tue) == 6);
9560     assert(daysToDayOfWeek(DayOfWeek.wed, DayOfWeek.wed) == 0);
9561     assert(daysToDayOfWeek(DayOfWeek.wed, DayOfWeek.thu) == 1);
9562     assert(daysToDayOfWeek(DayOfWeek.wed, DayOfWeek.fri) == 2);
9563     assert(daysToDayOfWeek(DayOfWeek.wed, DayOfWeek.sat) == 3);
9564
9565     assert(daysToDayOfWeek(DayOfWeek.thu, DayOfWeek.sun) == 3);
9566     assert(daysToDayOfWeek(DayOfWeek.thu, DayOfWeek.mon) == 4);
9567     assert(daysToDayOfWeek(DayOfWeek.thu, DayOfWeek.tue) == 5);
9568     assert(daysToDayOfWeek(DayOfWeek.thu, DayOfWeek.wed) == 6);
9569     assert(daysToDayOfWeek(DayOfWeek.thu, DayOfWeek.thu) == 0);
9570     assert(daysToDayOfWeek(DayOfWeek.thu, DayOfWeek.fri) == 1);
9571     assert(daysToDayOfWeek(DayOfWeek.thu, DayOfWeek.sat) == 2);
9572
9573     assert(daysToDayOfWeek(DayOfWeek.fri, DayOfWeek.sun) == 2);
9574     assert(daysToDayOfWeek(DayOfWeek.fri, DayOfWeek.mon) == 3);
9575     assert(daysToDayOfWeek(DayOfWeek.fri, DayOfWeek.tue) == 4);
9576     assert(daysToDayOfWeek(DayOfWeek.fri, DayOfWeek.wed) == 5);
9577     assert(daysToDayOfWeek(DayOfWeek.fri, DayOfWeek.thu) == 6);
9578     assert(daysToDayOfWeek(DayOfWeek.fri, DayOfWeek.fri) == 0);
9579     assert(daysToDayOfWeek(DayOfWeek.fri, DayOfWeek.sat) == 1);
9580
9581     assert(daysToDayOfWeek(DayOfWeek.sat, DayOfWeek.sun) == 1);
9582     assert(daysToDayOfWeek(DayOfWeek.sat, DayOfWeek.mon) == 2);
9583     assert(daysToDayOfWeek(DayOfWeek.sat, DayOfWeek.tue) == 3);
9584     assert(daysToDayOfWeek(DayOfWeek.sat, DayOfWeek.wed) == 4);
9585     assert(daysToDayOfWeek(DayOfWeek.sat, DayOfWeek.thu) == 5);
9586     assert(daysToDayOfWeek(DayOfWeek.sat, DayOfWeek.fri) == 6);
9587     assert(daysToDayOfWeek(DayOfWeek.sat, DayOfWeek.sat) == 0);
9588 }
9589
9590
9591 /++
9592     Returns the number of months from the current months of the year to the
9593     given month of the year. If they are the same, then the result is 0.
9594
9595     Params:
9596         currMonth = The current month of the year.
9597         month     = The month of the year to get the number of months to.
9598   +/
9599 int monthsToMonth(int currMonth, int month) @safe pure
9600 {
9601     enforceValid!"months"(currMonth);
9602     enforceValid!"months"(month);
9603
9604     if (currMonth == month)
9605         return 0;
9606     if (currMonth < month)
9607         return month - currMonth;
9608     return Month.dec - currMonth + month;
9609 }
9610
9611 ///
9612 @safe pure unittest
9613 {
9614     assert(monthsToMonth(Month.jan, Month.jan) == 0);
9615     assert(monthsToMonth(Month.jan, Month.dec) == 11);
9616     assert(monthsToMonth(Month.jul, Month.oct) == 3);
9617 }
9618
9619 @safe unittest
9620 {
9621     assert(monthsToMonth(Month.jan, Month.jan) == 0);
9622     assert(monthsToMonth(Month.jan, Month.feb) == 1);
9623     assert(monthsToMonth(Month.jan, Month.mar) == 2);
9624     assert(monthsToMonth(Month.jan, Month.apr) == 3);
9625     assert(monthsToMonth(Month.jan, Month.may) == 4);
9626     assert(monthsToMonth(Month.jan, Month.jun) == 5);
9627     assert(monthsToMonth(Month.jan, Month.jul) == 6);
9628     assert(monthsToMonth(Month.jan, Month.aug) == 7);
9629     assert(monthsToMonth(Month.jan, Month.sep) == 8);
9630     assert(monthsToMonth(Month.jan, Month.oct) == 9);
9631     assert(monthsToMonth(Month.jan, Month.nov) == 10);
9632     assert(monthsToMonth(Month.jan, Month.dec) == 11);
9633
9634     assert(monthsToMonth(Month.may, Month.jan) == 8);
9635     assert(monthsToMonth(Month.may, Month.feb) == 9);
9636     assert(monthsToMonth(Month.may, Month.mar) == 10);
9637     assert(monthsToMonth(Month.may, Month.apr) == 11);
9638     assert(monthsToMonth(Month.may, Month.may) == 0);
9639     assert(monthsToMonth(Month.may, Month.jun) == 1);
9640     assert(monthsToMonth(Month.may, Month.jul) == 2);
9641     assert(monthsToMonth(Month.may, Month.aug) == 3);
9642     assert(monthsToMonth(Month.may, Month.sep) == 4);
9643     assert(monthsToMonth(Month.may, Month.oct) == 5);
9644     assert(monthsToMonth(Month.may, Month.nov) == 6);
9645     assert(monthsToMonth(Month.may, Month.dec) == 7);
9646
9647     assert(monthsToMonth(Month.oct, Month.jan) == 3);
9648     assert(monthsToMonth(Month.oct, Month.feb) == 4);
9649     assert(monthsToMonth(Month.oct, Month.mar) == 5);
9650     assert(monthsToMonth(Month.oct, Month.apr) == 6);
9651     assert(monthsToMonth(Month.oct, Month.may) == 7);
9652     assert(monthsToMonth(Month.oct, Month.jun) == 8);
9653     assert(monthsToMonth(Month.oct, Month.jul) == 9);
9654     assert(monthsToMonth(Month.oct, Month.aug) == 10);
9655     assert(monthsToMonth(Month.oct, Month.sep) == 11);
9656     assert(monthsToMonth(Month.oct, Month.oct) == 0);
9657     assert(monthsToMonth(Month.oct, Month.nov) == 1);
9658     assert(monthsToMonth(Month.oct, Month.dec) == 2);
9659
9660     assert(monthsToMonth(Month.dec, Month.jan) == 1);
9661     assert(monthsToMonth(Month.dec, Month.feb) == 2);
9662     assert(monthsToMonth(Month.dec, Month.mar) == 3);
9663     assert(monthsToMonth(Month.dec, Month.apr) == 4);
9664     assert(monthsToMonth(Month.dec, Month.may) == 5);
9665     assert(monthsToMonth(Month.dec, Month.jun) == 6);
9666     assert(monthsToMonth(Month.dec, Month.jul) == 7);
9667     assert(monthsToMonth(Month.dec, Month.aug) == 8);
9668     assert(monthsToMonth(Month.dec, Month.sep) == 9);
9669     assert(monthsToMonth(Month.dec, Month.oct) == 10);
9670     assert(monthsToMonth(Month.dec, Month.nov) == 11);
9671     assert(monthsToMonth(Month.dec, Month.dec) == 0);
9672 }
9673
9674
9675 /++
9676     Whether the given Gregorian Year is a leap year.
9677
9678     Params:
9679         year = The year to to be tested.
9680  +/
9681 bool yearIsLeapYear(int year) @safe pure nothrow @nogc
9682 {
9683     if (year % 400 == 0)
9684         return true;
9685     if (year % 100 == 0)
9686         return false;
9687     return year % 4 == 0;
9688 }
9689
9690 ///
9691 @safe unittest
9692 {
9693     foreach (year; [1, 2, 100, 2001, 2002, 2003, 2005, 2006, 2007, 2009, 2010])
9694     {
9695         assert(!yearIsLeapYear(year));
9696         assert(!yearIsLeapYear(-year));
9697     }
9698
9699     foreach (year; [0, 4, 8, 400, 800, 1600, 1996, 2000, 2004, 2008, 2012])
9700     {
9701         assert(yearIsLeapYear(year));
9702         assert(yearIsLeapYear(-year));
9703     }
9704 }
9705
9706 @safe unittest
9707 {
9708     import std.format : format;
9709     foreach (year; [1, 2, 3, 5, 6, 7, 100, 200, 300, 500, 600, 700, 1998, 1999,
9710                     2001, 2002, 2003, 2005, 2006, 2007, 2009, 2010, 2011])
9711     {
9712         assert(!yearIsLeapYear(year), format("year: %s.", year));
9713         assert(!yearIsLeapYear(-year), format("year: %s.", year));
9714     }
9715
9716     foreach (year; [0, 4, 8, 400, 800, 1600, 1996, 2000, 2004, 2008, 2012])
9717     {
9718         assert(yearIsLeapYear(year), format("year: %s.", year));
9719         assert(yearIsLeapYear(-year), format("year: %s.", year));
9720     }
9721 }
9722
9723
9724 /++
9725     Whether the given type defines all of the necessary functions for it to
9726     function as a time point.
9727
9728     1. $(D T) must define a static property named $(D min) which is the smallest
9729        value of $(D T) as $(D Unqual!T).
9730
9731     2. $(D T) must define a static property named $(D max) which is the largest
9732        value of $(D T) as $(D Unqual!T).
9733
9734     3. $(D T) must define an $(D opBinary) for addition and subtraction that
9735        accepts $(REF Duration, core,time) and returns $(D Unqual!T).
9736
9737     4. $(D T) must define an $(D opOpAssign) for addition and subtraction that
9738        accepts $(REF Duration, core,time) and returns $(D ref Unqual!T).
9739
9740     5. $(D T) must define a $(D opBinary) for subtraction which accepts $(D T)
9741        and returns returns $(REF Duration, core,time).
9742   +/
9743 template isTimePoint(T)
9744 {
9745     import core.time : Duration;
9746     import std.traits : FunctionAttribute, functionAttributes, Unqual;
9747
9748     enum isTimePoint = hasMin &&
9749                        hasMax &&
9750                        hasOverloadedOpBinaryWithDuration &&
9751                        hasOverloadedOpAssignWithDuration &&
9752                        hasOverloadedOpBinaryWithSelf &&
9753                        !is(U == Duration);
9754
9755 private:
9756
9757     alias U = Unqual!T;
9758
9759     enum hasMin = __traits(hasMember, T, "min") &&
9760                   is(typeof(T.min) == U) &&
9761                   is(typeof({static assert(__traits(isStaticFunction, T.min));}));
9762
9763     enum hasMax = __traits(hasMember, T, "max") &&
9764                   is(typeof(T.max) == U) &&
9765                   is(typeof({static assert(__traits(isStaticFunction, T.max));}));
9766
9767     enum hasOverloadedOpBinaryWithDuration = is(typeof(T.init + Duration.init) == U) &&
9768                                              is(typeof(T.init - Duration.init) == U);
9769
9770     enum hasOverloadedOpAssignWithDuration = is(typeof(U.init += Duration.init) == U) &&
9771                                              is(typeof(U.init -= Duration.init) == U) &&
9772                                              is(typeof(
9773                                              {
9774                                                  // Until the overload with TickDuration is removed, this is ambiguous.
9775                                                  //alias add = U.opOpAssign!"+";
9776                                                  //alias sub = U.opOpAssign!"-";
9777                                                  U u;
9778                                                  auto ref add() { return u += Duration.init; }
9779                                                  auto ref sub() { return u -= Duration.init; }
9780                                                  alias FA = FunctionAttribute;
9781                                                  static assert((functionAttributes!add & FA.ref_) != 0);
9782                                                  static assert((functionAttributes!sub & FA.ref_) != 0);
9783                                              }));
9784
9785     enum hasOverloadedOpBinaryWithSelf = is(typeof(T.init - T.init) == Duration);
9786 }
9787
9788 ///
9789 @safe unittest
9790 {
9791     import core.time : Duration;
9792     import std.datetime.interval : Interval;
9793     import std.datetime.systime : SysTime;
9794
9795     static assert(isTimePoint!Date);
9796     static assert(isTimePoint!DateTime);
9797     static assert(isTimePoint!SysTime);
9798     static assert(isTimePoint!TimeOfDay);
9799
9800     static assert(!isTimePoint!int);
9801     static assert(!isTimePoint!Duration);
9802     static assert(!isTimePoint!(Interval!SysTime));
9803 }
9804
9805 @safe unittest
9806 {
9807     import core.time;
9808     import std.datetime.interval;
9809     import std.datetime.systime;
9810     import std.meta : AliasSeq;
9811
9812     foreach (TP; AliasSeq!(Date, DateTime, SysTime, TimeOfDay))
9813     {
9814         static assert(isTimePoint!(const TP), TP.stringof);
9815         static assert(isTimePoint!(immutable TP), TP.stringof);
9816     }
9817
9818     foreach (T; AliasSeq!(float, string, Duration, Interval!Date, PosInfInterval!Date, NegInfInterval!Date))
9819         static assert(!isTimePoint!T, T.stringof);
9820 }
9821
9822
9823 /++
9824     Whether all of the given strings are valid units of time.
9825
9826     $(D "nsecs") is not considered a valid unit of time. Nothing in std.datetime
9827     can handle precision greater than hnsecs, and the few functions in core.time
9828     which deal with "nsecs" deal with it explicitly.
9829   +/
9830 bool validTimeUnits(string[] units...) @safe pure nothrow @nogc
9831 {
9832     import std.algorithm.searching : canFind;
9833     foreach (str; units)
9834     {
9835         if (!canFind(timeStrings[], str))
9836             return false;
9837     }
9838     return true;
9839 }
9840
9841 ///
9842 @safe @nogc nothrow unittest
9843 {
9844     assert(validTimeUnits("msecs", "seconds", "minutes"));
9845     assert(validTimeUnits("days", "weeks", "months"));
9846     assert(!validTimeUnits("ms", "seconds", "minutes"));
9847 }
9848
9849
9850 /++
9851     Compares two time unit strings. $(D "years") are the largest units and
9852     $(D "hnsecs") are the smallest.
9853
9854     Returns:
9855         $(BOOKTABLE,
9856         $(TR $(TD this &lt; rhs) $(TD &lt; 0))
9857         $(TR $(TD this == rhs) $(TD 0))
9858         $(TR $(TD this &gt; rhs) $(TD &gt; 0))
9859         )
9860
9861     Throws:
9862         $(LREF DateTimeException) if either of the given strings is not a valid
9863         time unit string.
9864  +/
9865 int cmpTimeUnits(string lhs, string rhs) @safe pure
9866 {
9867     import std.algorithm.searching : countUntil;
9868     import std.exception : enforce;
9869     import std.format : format;
9870
9871     auto tstrings = timeStrings;
9872     immutable indexOfLHS = countUntil(tstrings, lhs);
9873     immutable indexOfRHS = countUntil(tstrings, rhs);
9874
9875     enforce(indexOfLHS != -1, format("%s is not a valid TimeString", lhs));
9876     enforce(indexOfRHS != -1, format("%s is not a valid TimeString", rhs));
9877
9878     if (indexOfLHS < indexOfRHS)
9879         return -1;
9880     if (indexOfLHS > indexOfRHS)
9881         return 1;
9882
9883     return 0;
9884 }
9885
9886 ///
9887 @safe pure unittest
9888 {
9889     assert(cmpTimeUnits("hours", "hours") == 0);
9890     assert(cmpTimeUnits("hours", "weeks") < 0);
9891     assert(cmpTimeUnits("months", "seconds") > 0);
9892 }
9893
9894 @safe unittest
9895 {
9896     foreach (i, outerUnits; timeStrings)
9897     {
9898         assert(cmpTimeUnits(outerUnits, outerUnits) == 0);
9899
9900         // For some reason, $ won't compile.
9901         foreach (innerUnits; timeStrings[i + 1 .. timeStrings.length])
9902             assert(cmpTimeUnits(outerUnits, innerUnits) == -1);
9903     }
9904
9905     foreach (i, outerUnits; timeStrings)
9906     {
9907         foreach (innerUnits; timeStrings[0 .. i])
9908             assert(cmpTimeUnits(outerUnits, innerUnits) == 1);
9909     }
9910 }
9911
9912
9913 /++
9914     Compares two time unit strings at compile time. $(D "years") are the largest
9915     units and $(D "hnsecs") are the smallest.
9916
9917     This template is used instead of $(D cmpTimeUnits) because exceptions
9918     can't be thrown at compile time and $(D cmpTimeUnits) must enforce that
9919     the strings it's given are valid time unit strings. This template uses a
9920     template constraint instead.
9921
9922     Returns:
9923         $(BOOKTABLE,
9924         $(TR $(TD this &lt; rhs) $(TD &lt; 0))
9925         $(TR $(TD this == rhs) $(TD 0))
9926         $(TR $(TD this &gt; rhs) $(TD &gt; 0))
9927         )
9928  +/
9929 template CmpTimeUnits(string lhs, string rhs)
9930 if (validTimeUnits(lhs, rhs))
9931 {
9932     enum CmpTimeUnits = cmpTimeUnitsCTFE(lhs, rhs);
9933 }
9934
9935
9936 // Helper function for CmpTimeUnits.
9937 private int cmpTimeUnitsCTFE(string lhs, string rhs) @safe pure nothrow @nogc
9938 {
9939     import std.algorithm.searching : countUntil;
9940     auto tstrings = timeStrings;
9941     immutable indexOfLHS = countUntil(tstrings, lhs);
9942     immutable indexOfRHS = countUntil(tstrings, rhs);
9943
9944     if (indexOfLHS < indexOfRHS)
9945         return -1;
9946     if (indexOfLHS > indexOfRHS)
9947         return 1;
9948
9949     return 0;
9950 }
9951
9952 @safe unittest
9953 {
9954     import std.format : format;
9955     import std.meta : AliasSeq;
9956
9957     static string genTest(size_t index)
9958     {
9959         auto currUnits = timeStrings[index];
9960         auto test = format(`assert(CmpTimeUnits!("%s", "%s") == 0);`, currUnits, currUnits);
9961
9962         foreach (units; timeStrings[index + 1 .. $])
9963             test ~= format(`assert(CmpTimeUnits!("%s", "%s") == -1);`, currUnits, units);
9964
9965         foreach (units; timeStrings[0 .. index])
9966             test ~= format(`assert(CmpTimeUnits!("%s", "%s") == 1);`, currUnits, units);
9967
9968         return test;
9969     }
9970
9971     static assert(timeStrings.length == 10);
9972     foreach (n; AliasSeq!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9))
9973         mixin(genTest(n));
9974 }
9975
9976
9977 package:
9978
9979
9980 /+
9981     Array of the short (three letter) names of each month.
9982   +/
9983 immutable string[12] _monthNames = ["Jan",
9984                                     "Feb",
9985                                     "Mar",
9986                                     "Apr",
9987                                     "May",
9988                                     "Jun",
9989                                     "Jul",
9990                                     "Aug",
9991                                     "Sep",
9992                                     "Oct",
9993                                     "Nov",
9994                                     "Dec"];
9995
9996 /+
9997     The maximum valid Day in the given month in the given year.
9998
9999     Params:
10000         year  = The year to get the day for.
10001         month = The month of the Gregorian Calendar to get the day for.
10002  +/
10003 ubyte maxDay(int year, int month) @safe pure nothrow @nogc
10004 in
10005 {
10006     assert(valid!"months"(month));
10007 }
10008 body
10009 {
10010     switch (month)
10011     {
10012         case Month.jan, Month.mar, Month.may, Month.jul, Month.aug, Month.oct, Month.dec:
10013             return 31;
10014         case Month.feb:
10015             return yearIsLeapYear(year) ? 29 : 28;
10016         case Month.apr, Month.jun, Month.sep, Month.nov:
10017             return 30;
10018         default:
10019             assert(0, "Invalid month.");
10020     }
10021 }
10022
10023 @safe unittest
10024 {
10025     // Test A.D.
10026     assert(maxDay(1999, 1) == 31);
10027     assert(maxDay(1999, 2) == 28);
10028     assert(maxDay(1999, 3) == 31);
10029     assert(maxDay(1999, 4) == 30);
10030     assert(maxDay(1999, 5) == 31);
10031     assert(maxDay(1999, 6) == 30);
10032     assert(maxDay(1999, 7) == 31);
10033     assert(maxDay(1999, 8) == 31);
10034     assert(maxDay(1999, 9) == 30);
10035     assert(maxDay(1999, 10) == 31);
10036     assert(maxDay(1999, 11) == 30);
10037     assert(maxDay(1999, 12) == 31);
10038
10039     assert(maxDay(2000, 1) == 31);
10040     assert(maxDay(2000, 2) == 29);
10041     assert(maxDay(2000, 3) == 31);
10042     assert(maxDay(2000, 4) == 30);
10043     assert(maxDay(2000, 5) == 31);
10044     assert(maxDay(2000, 6) == 30);
10045     assert(maxDay(2000, 7) == 31);
10046     assert(maxDay(2000, 8) == 31);
10047     assert(maxDay(2000, 9) == 30);
10048     assert(maxDay(2000, 10) == 31);
10049     assert(maxDay(2000, 11) == 30);
10050     assert(maxDay(2000, 12) == 31);
10051
10052     // Test B.C.
10053     assert(maxDay(-1999, 1) == 31);
10054     assert(maxDay(-1999, 2) == 28);
10055     assert(maxDay(-1999, 3) == 31);
10056     assert(maxDay(-1999, 4) == 30);
10057     assert(maxDay(-1999, 5) == 31);
10058     assert(maxDay(-1999, 6) == 30);
10059     assert(maxDay(-1999, 7) == 31);
10060     assert(maxDay(-1999, 8) == 31);
10061     assert(maxDay(-1999, 9) == 30);
10062     assert(maxDay(-1999, 10) == 31);
10063     assert(maxDay(-1999, 11) == 30);
10064     assert(maxDay(-1999, 12) == 31);
10065
10066     assert(maxDay(-2000, 1) == 31);
10067     assert(maxDay(-2000, 2) == 29);
10068     assert(maxDay(-2000, 3) == 31);
10069     assert(maxDay(-2000, 4) == 30);
10070     assert(maxDay(-2000, 5) == 31);
10071     assert(maxDay(-2000, 6) == 30);
10072     assert(maxDay(-2000, 7) == 31);
10073     assert(maxDay(-2000, 8) == 31);
10074     assert(maxDay(-2000, 9) == 30);
10075     assert(maxDay(-2000, 10) == 31);
10076     assert(maxDay(-2000, 11) == 30);
10077     assert(maxDay(-2000, 12) == 31);
10078 }
10079
10080 /+
10081     Splits out a particular unit from hnsecs and gives the value for that
10082     unit and the remaining hnsecs. It really shouldn't be used unless unless
10083     all units larger than the given units have already been split out.
10084
10085     Params:
10086         units  = The units to split out.
10087         hnsecs = The current total hnsecs. Upon returning, it is the hnsecs left
10088                  after splitting out the given units.
10089
10090     Returns:
10091         The number of the given units from converting hnsecs to those units.
10092   +/
10093 long splitUnitsFromHNSecs(string units)(ref long hnsecs) @safe pure nothrow @nogc
10094 if (validTimeUnits(units) && CmpTimeUnits!(units, "months") < 0)
10095 {
10096     import core.time : convert;
10097     immutable value = convert!("hnsecs", units)(hnsecs);
10098     hnsecs -= convert!(units, "hnsecs")(value);
10099     return value;
10100 }
10101
10102 @safe unittest
10103 {
10104     auto hnsecs = 2595000000007L;
10105     immutable days = splitUnitsFromHNSecs!"days"(hnsecs);
10106     assert(days == 3);
10107     assert(hnsecs == 3000000007);
10108
10109     immutable minutes = splitUnitsFromHNSecs!"minutes"(hnsecs);
10110     assert(minutes == 5);
10111     assert(hnsecs == 7);
10112 }
10113
10114
10115 /+
10116     Returns the day of the week for the given day of the Gregorian Calendar.
10117
10118     Params:
10119         day = The day of the Gregorian Calendar for which to get the day of
10120               the week.
10121   +/
10122 DayOfWeek getDayOfWeek(int day) @safe pure nothrow @nogc
10123 {
10124     // January 1st, 1 A.D. was a Monday
10125     if (day >= 0)
10126         return cast(DayOfWeek)(day % 7);
10127     else
10128     {
10129         immutable dow = cast(DayOfWeek)((day % 7) + 7);
10130
10131         if (dow == 7)
10132             return DayOfWeek.sun;
10133         else
10134             return dow;
10135     }
10136 }
10137
10138 @safe unittest
10139 {
10140     import std.datetime.systime : SysTime;
10141
10142     // Test A.D.
10143     assert(getDayOfWeek(SysTime(Date(1, 1, 1)).dayOfGregorianCal) == DayOfWeek.mon);
10144     assert(getDayOfWeek(SysTime(Date(1, 1, 2)).dayOfGregorianCal) == DayOfWeek.tue);
10145     assert(getDayOfWeek(SysTime(Date(1, 1, 3)).dayOfGregorianCal) == DayOfWeek.wed);
10146     assert(getDayOfWeek(SysTime(Date(1, 1, 4)).dayOfGregorianCal) == DayOfWeek.thu);
10147     assert(getDayOfWeek(SysTime(Date(1, 1, 5)).dayOfGregorianCal) == DayOfWeek.fri);
10148     assert(getDayOfWeek(SysTime(Date(1, 1, 6)).dayOfGregorianCal) == DayOfWeek.sat);
10149     assert(getDayOfWeek(SysTime(Date(1, 1, 7)).dayOfGregorianCal) == DayOfWeek.sun);
10150     assert(getDayOfWeek(SysTime(Date(1, 1, 8)).dayOfGregorianCal) == DayOfWeek.mon);
10151     assert(getDayOfWeek(SysTime(Date(1, 1, 9)).dayOfGregorianCal) == DayOfWeek.tue);
10152     assert(getDayOfWeek(SysTime(Date(2, 1, 1)).dayOfGregorianCal) == DayOfWeek.tue);
10153     assert(getDayOfWeek(SysTime(Date(3, 1, 1)).dayOfGregorianCal) == DayOfWeek.wed);
10154     assert(getDayOfWeek(SysTime(Date(4, 1, 1)).dayOfGregorianCal) == DayOfWeek.thu);
10155     assert(getDayOfWeek(SysTime(Date(5, 1, 1)).dayOfGregorianCal) == DayOfWeek.sat);
10156     assert(getDayOfWeek(SysTime(Date(2000, 1, 1)).dayOfGregorianCal) == DayOfWeek.sat);
10157     assert(getDayOfWeek(SysTime(Date(2010, 8, 22)).dayOfGregorianCal) == DayOfWeek.sun);
10158     assert(getDayOfWeek(SysTime(Date(2010, 8, 23)).dayOfGregorianCal) == DayOfWeek.mon);
10159     assert(getDayOfWeek(SysTime(Date(2010, 8, 24)).dayOfGregorianCal) == DayOfWeek.tue);
10160     assert(getDayOfWeek(SysTime(Date(2010, 8, 25)).dayOfGregorianCal) == DayOfWeek.wed);
10161     assert(getDayOfWeek(SysTime(Date(2010, 8, 26)).dayOfGregorianCal) == DayOfWeek.thu);
10162     assert(getDayOfWeek(SysTime(Date(2010, 8, 27)).dayOfGregorianCal) == DayOfWeek.fri);
10163     assert(getDayOfWeek(SysTime(Date(2010, 8, 28)).dayOfGregorianCal) == DayOfWeek.sat);
10164     assert(getDayOfWeek(SysTime(Date(2010, 8, 29)).dayOfGregorianCal) == DayOfWeek.sun);
10165
10166     // Test B.C.
10167     assert(getDayOfWeek(SysTime(Date(0, 12, 31)).dayOfGregorianCal) == DayOfWeek.sun);
10168     assert(getDayOfWeek(SysTime(Date(0, 12, 30)).dayOfGregorianCal) == DayOfWeek.sat);
10169     assert(getDayOfWeek(SysTime(Date(0, 12, 29)).dayOfGregorianCal) == DayOfWeek.fri);
10170     assert(getDayOfWeek(SysTime(Date(0, 12, 28)).dayOfGregorianCal) == DayOfWeek.thu);
10171     assert(getDayOfWeek(SysTime(Date(0, 12, 27)).dayOfGregorianCal) == DayOfWeek.wed);
10172     assert(getDayOfWeek(SysTime(Date(0, 12, 26)).dayOfGregorianCal) == DayOfWeek.tue);
10173     assert(getDayOfWeek(SysTime(Date(0, 12, 25)).dayOfGregorianCal) == DayOfWeek.mon);
10174     assert(getDayOfWeek(SysTime(Date(0, 12, 24)).dayOfGregorianCal) == DayOfWeek.sun);
10175     assert(getDayOfWeek(SysTime(Date(0, 12, 23)).dayOfGregorianCal) == DayOfWeek.sat);
10176 }
10177
10178
10179 private:
10180
10181 enum daysInYear     = 365;  // The number of days in a non-leap year.
10182 enum daysInLeapYear = 366;  // The numbef or days in a leap year.
10183 enum daysIn4Years   = daysInYear * 3 + daysInLeapYear;  // Number of days in 4 years.
10184 enum daysIn100Years = daysIn4Years * 25 - 1;  // The number of days in 100 years.
10185 enum daysIn400Years = daysIn100Years * 4 + 1; // The number of days in 400 years.
10186
10187 /+
10188     Array of integers representing the last days of each month in a year.
10189   +/
10190 immutable int[13] lastDayNonLeap = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365];
10191
10192 /+
10193     Array of integers representing the last days of each month in a leap year.
10194   +/
10195 immutable int[13] lastDayLeap = [0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366];
10196
10197
10198 /+
10199     Returns the string representation of the given month.
10200   +/
10201 string monthToString(Month month) @safe pure
10202 {
10203     import std.format : format;
10204     assert(month >= Month.jan && month <= Month.dec, format("Invalid month: %s", month));
10205     return _monthNames[month - Month.jan];
10206 }
10207
10208 @safe unittest
10209 {
10210     assert(monthToString(Month.jan) == "Jan");
10211     assert(monthToString(Month.feb) == "Feb");
10212     assert(monthToString(Month.mar) == "Mar");
10213     assert(monthToString(Month.apr) == "Apr");
10214     assert(monthToString(Month.may) == "May");
10215     assert(monthToString(Month.jun) == "Jun");
10216     assert(monthToString(Month.jul) == "Jul");
10217     assert(monthToString(Month.aug) == "Aug");
10218     assert(monthToString(Month.sep) == "Sep");
10219     assert(monthToString(Month.oct) == "Oct");
10220     assert(monthToString(Month.nov) == "Nov");
10221     assert(monthToString(Month.dec) == "Dec");
10222 }
10223
10224
10225 /+
10226     Returns the Month corresponding to the given string.
10227
10228     Params:
10229         monthStr = The string representation of the month to get the Month for.
10230
10231     Throws:
10232         $(REF DateTimeException,std,datetime,date) if the given month is not a
10233         valid month string.
10234   +/
10235 Month monthFromString(string monthStr) @safe pure
10236 {
10237     import std.format : format;
10238     switch (monthStr)
10239     {
10240         case "Jan":
10241             return Month.jan;
10242         case "Feb":
10243             return Month.feb;
10244         case "Mar":
10245             return Month.mar;
10246         case "Apr":
10247             return Month.apr;
10248         case "May":
10249             return Month.may;
10250         case "Jun":
10251             return Month.jun;
10252         case "Jul":
10253             return Month.jul;
10254         case "Aug":
10255             return Month.aug;
10256         case "Sep":
10257             return Month.sep;
10258         case "Oct":
10259             return Month.oct;
10260         case "Nov":
10261             return Month.nov;
10262         case "Dec":
10263             return Month.dec;
10264         default:
10265             throw new DateTimeException(format("Invalid month %s", monthStr));
10266     }
10267 }
10268
10269 @safe unittest
10270 {
10271     import std.stdio : writeln;
10272     import std.traits : EnumMembers;
10273     foreach (badStr; ["Ja", "Janu", "Januar", "Januarys", "JJanuary", "JANUARY",
10274                       "JAN", "january", "jaNuary", "jaN", "jaNuaRy", "jAn"])
10275     {
10276         scope(failure) writeln(badStr);
10277         assertThrown!DateTimeException(monthFromString(badStr));
10278     }
10279
10280     foreach (month; EnumMembers!Month)
10281     {
10282         scope(failure) writeln(month);
10283         assert(monthFromString(monthToString(month)) == month);
10284     }
10285 }
10286
10287
10288 version (unittest)
10289 {
10290     // All of these helper arrays are sorted in ascending order.
10291     auto testYearsBC = [-1999, -1200, -600, -4, -1, 0];
10292     auto testYearsAD = [1, 4, 1000, 1999, 2000, 2012];
10293
10294     // I'd use a Tuple, but I get forward reference errors if I try.
10295     struct MonthDay
10296     {
10297         Month month;
10298         short day;
10299
10300         this(int m, short d)
10301         {
10302             month = cast(Month) m;
10303             day = d;
10304         }
10305     }
10306
10307     MonthDay[] testMonthDays = [MonthDay(1, 1),
10308                                 MonthDay(1, 2),
10309                                 MonthDay(3, 17),
10310                                 MonthDay(7, 4),
10311                                 MonthDay(10, 27),
10312                                 MonthDay(12, 30),
10313                                 MonthDay(12, 31)];
10314
10315     auto testDays = [1, 2, 9, 10, 16, 20, 25, 28, 29, 30, 31];
10316
10317     auto testTODs = [TimeOfDay(0, 0, 0),
10318                      TimeOfDay(0, 0, 1),
10319                      TimeOfDay(0, 1, 0),
10320                      TimeOfDay(1, 0, 0),
10321                      TimeOfDay(13, 13, 13),
10322                      TimeOfDay(23, 59, 59)];
10323
10324     auto testHours = [0, 1, 12, 22, 23];
10325     auto testMinSecs = [0, 1, 30, 58, 59];
10326
10327     // Throwing exceptions is incredibly expensive, so we want to use a smaller
10328     // set of values for tests using assertThrown.
10329     auto testTODsThrown = [TimeOfDay(0, 0, 0),
10330                            TimeOfDay(13, 13, 13),
10331                            TimeOfDay(23, 59, 59)];
10332
10333     Date[] testDatesBC;
10334     Date[] testDatesAD;
10335
10336     DateTime[] testDateTimesBC;
10337     DateTime[] testDateTimesAD;
10338
10339     // I'd use a Tuple, but I get forward reference errors if I try.
10340     struct GregDay { int day; Date date; }
10341     auto testGregDaysBC = [GregDay(-1_373_427, Date(-3760, 9, 7)), // Start of the Hebrew Calendar
10342                            GregDay(-735_233, Date(-2012, 1, 1)),
10343                            GregDay(-735_202, Date(-2012, 2, 1)),
10344                            GregDay(-735_175, Date(-2012, 2, 28)),
10345                            GregDay(-735_174, Date(-2012, 2, 29)),
10346                            GregDay(-735_173, Date(-2012, 3, 1)),
10347                            GregDay(-734_502, Date(-2010, 1, 1)),
10348                            GregDay(-734_472, Date(-2010, 1, 31)),
10349                            GregDay(-734_471, Date(-2010, 2, 1)),
10350                            GregDay(-734_444, Date(-2010, 2, 28)),
10351                            GregDay(-734_443, Date(-2010, 3, 1)),
10352                            GregDay(-734_413, Date(-2010, 3, 31)),
10353                            GregDay(-734_412, Date(-2010, 4, 1)),
10354                            GregDay(-734_383, Date(-2010, 4, 30)),
10355                            GregDay(-734_382, Date(-2010, 5, 1)),
10356                            GregDay(-734_352, Date(-2010, 5, 31)),
10357                            GregDay(-734_351, Date(-2010, 6, 1)),
10358                            GregDay(-734_322, Date(-2010, 6, 30)),
10359                            GregDay(-734_321, Date(-2010, 7, 1)),
10360                            GregDay(-734_291, Date(-2010, 7, 31)),
10361                            GregDay(-734_290, Date(-2010, 8, 1)),
10362                            GregDay(-734_260, Date(-2010, 8, 31)),
10363                            GregDay(-734_259, Date(-2010, 9, 1)),
10364                            GregDay(-734_230, Date(-2010, 9, 30)),
10365                            GregDay(-734_229, Date(-2010, 10, 1)),
10366                            GregDay(-734_199, Date(-2010, 10, 31)),
10367                            GregDay(-734_198, Date(-2010, 11, 1)),
10368                            GregDay(-734_169, Date(-2010, 11, 30)),
10369                            GregDay(-734_168, Date(-2010, 12, 1)),
10370                            GregDay(-734_139, Date(-2010, 12, 30)),
10371                            GregDay(-734_138, Date(-2010, 12, 31)),
10372                            GregDay(-731_215, Date(-2001, 1, 1)),
10373                            GregDay(-730_850, Date(-2000, 1, 1)),
10374                            GregDay(-730_849, Date(-2000, 1, 2)),
10375                            GregDay(-730_486, Date(-2000, 12, 30)),
10376                            GregDay(-730_485, Date(-2000, 12, 31)),
10377                            GregDay(-730_484, Date(-1999, 1, 1)),
10378                            GregDay(-694_690, Date(-1901, 1, 1)),
10379                            GregDay(-694_325, Date(-1900, 1, 1)),
10380                            GregDay(-585_118, Date(-1601, 1, 1)),
10381                            GregDay(-584_753, Date(-1600, 1, 1)),
10382                            GregDay(-584_388, Date(-1600, 12, 31)),
10383                            GregDay(-584_387, Date(-1599, 1, 1)),
10384                            GregDay(-365_972, Date(-1001, 1, 1)),
10385                            GregDay(-365_607, Date(-1000, 1, 1)),
10386                            GregDay(-183_351, Date(-501, 1, 1)),
10387                            GregDay(-182_986, Date(-500, 1, 1)),
10388                            GregDay(-182_621, Date(-499, 1, 1)),
10389                            GregDay(-146_827, Date(-401, 1, 1)),
10390                            GregDay(-146_462, Date(-400, 1, 1)),
10391                            GregDay(-146_097, Date(-400, 12, 31)),
10392                            GregDay(-110_302, Date(-301, 1, 1)),
10393                            GregDay(-109_937, Date(-300, 1, 1)),
10394                            GregDay(-73_778, Date(-201, 1, 1)),
10395                            GregDay(-73_413, Date(-200, 1, 1)),
10396                            GregDay(-38_715, Date(-105, 1, 1)),
10397                            GregDay(-37_254, Date(-101, 1, 1)),
10398                            GregDay(-36_889, Date(-100, 1, 1)),
10399                            GregDay(-36_524, Date(-99, 1, 1)),
10400                            GregDay(-36_160, Date(-99, 12, 31)),
10401                            GregDay(-35_794, Date(-97, 1, 1)),
10402                            GregDay(-18_627, Date(-50, 1, 1)),
10403                            GregDay(-18_262, Date(-49, 1, 1)),
10404                            GregDay(-3652, Date(-9, 1, 1)),
10405                            GregDay(-2191, Date(-5, 1, 1)),
10406                            GregDay(-1827, Date(-5, 12, 31)),
10407                            GregDay(-1826, Date(-4, 1, 1)),
10408                            GregDay(-1825, Date(-4, 1, 2)),
10409                            GregDay(-1462, Date(-4, 12, 30)),
10410                            GregDay(-1461, Date(-4, 12, 31)),
10411                            GregDay(-1460, Date(-3, 1, 1)),
10412                            GregDay(-1096, Date(-3, 12, 31)),
10413                            GregDay(-1095, Date(-2, 1, 1)),
10414                            GregDay(-731, Date(-2, 12, 31)),
10415                            GregDay(-730, Date(-1, 1, 1)),
10416                            GregDay(-367, Date(-1, 12, 30)),
10417                            GregDay(-366, Date(-1, 12, 31)),
10418                            GregDay(-365, Date(0, 1, 1)),
10419                            GregDay(-31, Date(0, 11, 30)),
10420                            GregDay(-30, Date(0, 12, 1)),
10421                            GregDay(-1, Date(0, 12, 30)),
10422                            GregDay(0, Date(0, 12, 31))];
10423
10424     auto testGregDaysAD = [GregDay(1, Date(1, 1, 1)),
10425                            GregDay(2, Date(1, 1, 2)),
10426                            GregDay(32, Date(1, 2, 1)),
10427                            GregDay(365, Date(1, 12, 31)),
10428                            GregDay(366, Date(2, 1, 1)),
10429                            GregDay(731, Date(3, 1, 1)),
10430                            GregDay(1096, Date(4, 1, 1)),
10431                            GregDay(1097, Date(4, 1, 2)),
10432                            GregDay(1460, Date(4, 12, 30)),
10433                            GregDay(1461, Date(4, 12, 31)),
10434                            GregDay(1462, Date(5, 1, 1)),
10435                            GregDay(17_898, Date(50, 1, 1)),
10436                            GregDay(35_065, Date(97, 1, 1)),
10437                            GregDay(36_160, Date(100, 1, 1)),
10438                            GregDay(36_525, Date(101, 1, 1)),
10439                            GregDay(37_986, Date(105, 1, 1)),
10440                            GregDay(72_684, Date(200, 1, 1)),
10441                            GregDay(73_049, Date(201, 1, 1)),
10442                            GregDay(109_208, Date(300, 1, 1)),
10443                            GregDay(109_573, Date(301, 1, 1)),
10444                            GregDay(145_732, Date(400, 1, 1)),
10445                            GregDay(146_098, Date(401, 1, 1)),
10446                            GregDay(182_257, Date(500, 1, 1)),
10447                            GregDay(182_622, Date(501, 1, 1)),
10448                            GregDay(364_878, Date(1000, 1, 1)),
10449                            GregDay(365_243, Date(1001, 1, 1)),
10450                            GregDay(584_023, Date(1600, 1, 1)),
10451                            GregDay(584_389, Date(1601, 1, 1)),
10452                            GregDay(693_596, Date(1900, 1, 1)),
10453                            GregDay(693_961, Date(1901, 1, 1)),
10454                            GregDay(729_755, Date(1999, 1, 1)),
10455                            GregDay(730_120, Date(2000, 1, 1)),
10456                            GregDay(730_121, Date(2000, 1, 2)),
10457                            GregDay(730_484, Date(2000, 12, 30)),
10458                            GregDay(730_485, Date(2000, 12, 31)),
10459                            GregDay(730_486, Date(2001, 1, 1)),
10460                            GregDay(733_773, Date(2010, 1, 1)),
10461                            GregDay(733_774, Date(2010, 1, 2)),
10462                            GregDay(733_803, Date(2010, 1, 31)),
10463                            GregDay(733_804, Date(2010, 2, 1)),
10464                            GregDay(733_831, Date(2010, 2, 28)),
10465                            GregDay(733_832, Date(2010, 3, 1)),
10466                            GregDay(733_862, Date(2010, 3, 31)),
10467                            GregDay(733_863, Date(2010, 4, 1)),
10468                            GregDay(733_892, Date(2010, 4, 30)),
10469                            GregDay(733_893, Date(2010, 5, 1)),
10470                            GregDay(733_923, Date(2010, 5, 31)),
10471                            GregDay(733_924, Date(2010, 6, 1)),
10472                            GregDay(733_953, Date(2010, 6, 30)),
10473                            GregDay(733_954, Date(2010, 7, 1)),
10474                            GregDay(733_984, Date(2010, 7, 31)),
10475                            GregDay(733_985, Date(2010, 8, 1)),
10476                            GregDay(734_015, Date(2010, 8, 31)),
10477                            GregDay(734_016, Date(2010, 9, 1)),
10478                            GregDay(734_045, Date(2010, 9, 30)),
10479                            GregDay(734_046, Date(2010, 10, 1)),
10480                            GregDay(734_076, Date(2010, 10, 31)),
10481                            GregDay(734_077, Date(2010, 11, 1)),
10482                            GregDay(734_106, Date(2010, 11, 30)),
10483                            GregDay(734_107, Date(2010, 12, 1)),
10484                            GregDay(734_136, Date(2010, 12, 30)),
10485                            GregDay(734_137, Date(2010, 12, 31)),
10486                            GregDay(734_503, Date(2012, 1, 1)),
10487                            GregDay(734_534, Date(2012, 2, 1)),
10488                            GregDay(734_561, Date(2012, 2, 28)),
10489                            GregDay(734_562, Date(2012, 2, 29)),
10490                            GregDay(734_563, Date(2012, 3, 1)),
10491                            GregDay(734_858, Date(2012, 12, 21))];
10492
10493     // I'd use a Tuple, but I get forward reference errors if I try.
10494     struct DayOfYear { int day; MonthDay md; }
10495     auto testDaysOfYear = [DayOfYear(1, MonthDay(1, 1)),
10496                            DayOfYear(2, MonthDay(1, 2)),
10497                            DayOfYear(3, MonthDay(1, 3)),
10498                            DayOfYear(31, MonthDay(1, 31)),
10499                            DayOfYear(32, MonthDay(2, 1)),
10500                            DayOfYear(59, MonthDay(2, 28)),
10501                            DayOfYear(60, MonthDay(3, 1)),
10502                            DayOfYear(90, MonthDay(3, 31)),
10503                            DayOfYear(91, MonthDay(4, 1)),
10504                            DayOfYear(120, MonthDay(4, 30)),
10505                            DayOfYear(121, MonthDay(5, 1)),
10506                            DayOfYear(151, MonthDay(5, 31)),
10507                            DayOfYear(152, MonthDay(6, 1)),
10508                            DayOfYear(181, MonthDay(6, 30)),
10509                            DayOfYear(182, MonthDay(7, 1)),
10510                            DayOfYear(212, MonthDay(7, 31)),
10511                            DayOfYear(213, MonthDay(8, 1)),
10512                            DayOfYear(243, MonthDay(8, 31)),
10513                            DayOfYear(244, MonthDay(9, 1)),
10514                            DayOfYear(273, MonthDay(9, 30)),
10515                            DayOfYear(274, MonthDay(10, 1)),
10516                            DayOfYear(304, MonthDay(10, 31)),
10517                            DayOfYear(305, MonthDay(11, 1)),
10518                            DayOfYear(334, MonthDay(11, 30)),
10519                            DayOfYear(335, MonthDay(12, 1)),
10520                            DayOfYear(363, MonthDay(12, 29)),
10521                            DayOfYear(364, MonthDay(12, 30)),
10522                            DayOfYear(365, MonthDay(12, 31))];
10523
10524     auto testDaysOfLeapYear = [DayOfYear(1, MonthDay(1, 1)),
10525                                DayOfYear(2, MonthDay(1, 2)),
10526                                DayOfYear(3, MonthDay(1, 3)),
10527                                DayOfYear(31, MonthDay(1, 31)),
10528                                DayOfYear(32, MonthDay(2, 1)),
10529                                DayOfYear(59, MonthDay(2, 28)),
10530                                DayOfYear(60, MonthDay(2, 29)),
10531                                DayOfYear(61, MonthDay(3, 1)),
10532                                DayOfYear(91, MonthDay(3, 31)),
10533                                DayOfYear(92, MonthDay(4, 1)),
10534                                DayOfYear(121, MonthDay(4, 30)),
10535                                DayOfYear(122, MonthDay(5, 1)),
10536                                DayOfYear(152, MonthDay(5, 31)),
10537                                DayOfYear(153, MonthDay(6, 1)),
10538                                DayOfYear(182, MonthDay(6, 30)),
10539                                DayOfYear(183, MonthDay(7, 1)),
10540                                DayOfYear(213, MonthDay(7, 31)),
10541                                DayOfYear(214, MonthDay(8, 1)),
10542                                DayOfYear(244, MonthDay(8, 31)),
10543                                DayOfYear(245, MonthDay(9, 1)),
10544                                DayOfYear(274, MonthDay(9, 30)),
10545                                DayOfYear(275, MonthDay(10, 1)),
10546                                DayOfYear(305, MonthDay(10, 31)),
10547                                DayOfYear(306, MonthDay(11, 1)),
10548                                DayOfYear(335, MonthDay(11, 30)),
10549                                DayOfYear(336, MonthDay(12, 1)),
10550                                DayOfYear(364, MonthDay(12, 29)),
10551                                DayOfYear(365, MonthDay(12, 30)),
10552                                DayOfYear(366, MonthDay(12, 31))];
10553
10554     void initializeTests() @safe
10555     {
10556         foreach (year; testYearsBC)
10557         {
10558             foreach (md; testMonthDays)
10559                 testDatesBC ~= Date(year, md.month, md.day);
10560         }
10561
10562         foreach (year; testYearsAD)
10563         {
10564             foreach (md; testMonthDays)
10565                 testDatesAD ~= Date(year, md.month, md.day);
10566         }
10567
10568         foreach (dt; testDatesBC)
10569         {
10570             foreach (tod; testTODs)
10571                 testDateTimesBC ~= DateTime(dt, tod);
10572         }
10573
10574         foreach (dt; testDatesAD)
10575         {
10576             foreach (tod; testTODs)
10577                 testDateTimesAD ~= DateTime(dt, tod);
10578         }
10579     }
10580 }