drivers/rtc/date.c

   1 /*
   2  * (C) Copyright 2001
   3  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   4  *
   5  * SPDX-License-Identifier:     GPL-2.0+
   6  */
   7
   8 /*
   9  * Date & Time support for Philips PCF8563 RTC
  10  */
  11
  12 #include <common.h>
  13 #include <command.h>
  14 #include <errno.h>
  15 #include <rtc.h>
  16
  17 #if defined(CONFIG_CMD_DATE) || defined(CONFIG_TIMESTAMP)
  18
  19 #define FEBRUARY                2
  20 #define STARTOFTIME             1970
  21 #define SECDAY                  86400L
  22 #define SECYR                   (SECDAY * 365)
  23 #define leapyear(year)          ((year) % 4 == 0)
  24 #define days_in_year(a)         (leapyear(a) ? 366 : 365)
  25 #define days_in_month(a)        (month_days[(a) - 1])
  26
  27 static int month_days[12] = {
  28         31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  29 };
  30
  31 /*
  32  * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
  33  */
  34 int rtc_calc_weekday(struct rtc_time *tm)
  35 {
  36         int leapsToDate;
  37         int lastYear;
  38         int day;
  39         int MonthOffset[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };
  40
  41         if (tm->tm_year < 1753)
  42                 return -EINVAL;
  43         lastYear=tm->tm_year-1;
  44
  45         /*
  46          * Number of leap corrections to apply up to end of last year
  47          */
  48         leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;
  49
  50         /*
  51          * This year is a leap year if it is divisible by 4 except when it is
  52          * divisible by 100 unless it is divisible by 400
  53          *
  54          * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
  55          */
  56         if((tm->tm_year%4==0) &&
  57            ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&
  58            (tm->tm_mon>2)) {
  59                 /*
  60                  * We are past Feb. 29 in a leap year
  61                  */
  62                 day=1;
  63         } else {
  64                 day=0;
  65         }
  66
  67         day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] + tm->tm_mday;
  68
  69         tm->tm_wday=day%7;
  70
  71         return 0;
  72 }
  73
  74 int rtc_to_tm(int tim, struct rtc_time *tm)
  75 {
  76         register int    i;
  77         register long   hms, day;
  78
  79         day = tim / SECDAY;
  80         hms = tim % SECDAY;
  81
  82         /* Hours, minutes, seconds are easy */
  83         tm->tm_hour = hms / 3600;
  84         tm->tm_min = (hms % 3600) / 60;
  85         tm->tm_sec = (hms % 3600) % 60;
  86
  87         /* Number of years in days */
  88         for (i = STARTOFTIME; day >= days_in_year(i); i++) {
  89                 day -= days_in_year(i);
  90         }
  91         tm->tm_year = i;
  92
  93         /* Number of months in days left */
  94         if (leapyear(tm->tm_year)) {
  95                 days_in_month(FEBRUARY) = 29;
  96         }
  97         for (i = 1; day >= days_in_month(i); i++) {
  98                 day -= days_in_month(i);
  99         }
 100         days_in_month(FEBRUARY) = 28;
 101         tm->tm_mon = i;
 102
 103         /* Days are what is left over (+1) from all that. */
 104         tm->tm_mday = day + 1;
 105
 106         /* Zero unused fields */
 107         tm->tm_yday = 0;
 108         tm->tm_isdst = 0;
 109
 110         /*
 111          * Determine the day of week
 112          */
 113         return rtc_calc_weekday(tm);
 114 }
 115
 116 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
 117  * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
 118  * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
 119  *
 120  * [For the Julian calendar (which was used in Russia before 1917,
 121  * Britain & colonies before 1752, anywhere else before 1582,
 122  * and is still in use by some communities) leave out the
 123  * -year/100+year/400 terms, and add 10.]
 124  *
 125  * This algorithm was first published by Gauss (I think).
 126  *
 127  * WARNING: this function will overflow on 2106-02-07 06:28:16 on
 128  * machines were long is 32-bit! (However, as time_t is signed, we
 129  * will already get problems at other places on 2038-01-19 03:14:08)
 130  */
 131 unsigned long
 132 mktime (unsigned int year, unsigned int mon,
 133         unsigned int day, unsigned int hour,
 134         unsigned int min, unsigned int sec)
 135 {
 136         if (0 >= (int) (mon -= 2)) {    /* 1..12 -> 11,12,1..10 */
 137                 mon += 12;              /* Puts Feb last since it has leap day */
 138                 year -= 1;
 139         }
 140
 141         return (((
 142                 (unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) +
 143                         year*365 - 719499
 144             )*24 + hour /* now have hours */
 145           )*60 + min /* now have minutes */
 146         )*60 + sec; /* finally seconds */
 147 }
 148
 149 #endif