drivers/rtc/date.c

   1 /*
   2  * (C) Copyright 2001
   3  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 /*
  25  * Date & Time support for Philips PCF8563 RTC
  26  */
  27
  28 #include <common.h>
  29 #include <command.h>
  30 #include <rtc.h>
  31
  32 #if defined(CONFIG_CMD_DATE) || defined(CONFIG_TIMESTAMP)
  33
  34 #define FEBRUARY                2
  35 #define STARTOFTIME             1970
  36 #define SECDAY                  86400L
  37 #define SECYR                   (SECDAY * 365)
  38 #define leapyear(year)          ((year) % 4 == 0)
  39 #define days_in_year(a)         (leapyear(a) ? 366 : 365)
  40 #define days_in_month(a)        (month_days[(a) - 1])
  41
  42 static int month_days[12] = {
  43         31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  44 };
  45
  46 /*
  47  * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
  48  */
  49 void GregorianDay(struct rtc_time * tm)
  50 {
  51         int leapsToDate;
  52         int lastYear;
  53         int day;
  54         int MonthOffset[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };
  55
  56         lastYear=tm->tm_year-1;
  57
  58         /*
  59          * Number of leap corrections to apply up to end of last year
  60          */
  61         leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;
  62
  63         /*
  64          * This year is a leap year if it is divisible by 4 except when it is
  65          * divisible by 100 unless it is divisible by 400
  66          *
  67          * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
  68          */
  69         if((tm->tm_year%4==0) &&
  70            ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&
  71            (tm->tm_mon>2)) {
  72                 /*
  73                  * We are past Feb. 29 in a leap year
  74                  */
  75                 day=1;
  76         } else {
  77                 day=0;
  78         }
  79
  80         day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] + tm->tm_mday;
  81
  82         tm->tm_wday=day%7;
  83 }
  84
  85 void to_tm(int tim, struct rtc_time * tm)
  86 {
  87         register int    i;
  88         register long   hms, day;
  89
  90         day = tim / SECDAY;
  91         hms = tim % SECDAY;
  92
  93         /* Hours, minutes, seconds are easy */
  94         tm->tm_hour = hms / 3600;
  95         tm->tm_min = (hms % 3600) / 60;
  96         tm->tm_sec = (hms % 3600) % 60;
  97
  98         /* Number of years in days */
  99         for (i = STARTOFTIME; day >= days_in_year(i); i++) {
 100                 day -= days_in_year(i);
 101         }
 102         tm->tm_year = i;
 103
 104         /* Number of months in days left */
 105         if (leapyear(tm->tm_year)) {
 106                 days_in_month(FEBRUARY) = 29;
 107         }
 108         for (i = 1; day >= days_in_month(i); i++) {
 109                 day -= days_in_month(i);
 110         }
 111         days_in_month(FEBRUARY) = 28;
 112         tm->tm_mon = i;
 113
 114         /* Days are what is left over (+1) from all that. */
 115         tm->tm_mday = day + 1;
 116
 117         /*
 118          * Determine the day of week
 119          */
 120         GregorianDay(tm);
 121 }
 122
 123 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
 124  * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
 125  * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
 126  *
 127  * [For the Julian calendar (which was used in Russia before 1917,
 128  * Britain & colonies before 1752, anywhere else before 1582,
 129  * and is still in use by some communities) leave out the
 130  * -year/100+year/400 terms, and add 10.]
 131  *
 132  * This algorithm was first published by Gauss (I think).
 133  *
 134  * WARNING: this function will overflow on 2106-02-07 06:28:16 on
 135  * machines were long is 32-bit! (However, as time_t is signed, we
 136  * will already get problems at other places on 2038-01-19 03:14:08)
 137  */
 138 unsigned long
 139 mktime (unsigned int year, unsigned int mon,
 140         unsigned int day, unsigned int hour,
 141         unsigned int min, unsigned int sec)
 142 {
 143         if (0 >= (int) (mon -= 2)) {    /* 1..12 -> 11,12,1..10 */
 144                 mon += 12;              /* Puts Feb last since it has leap day */
 145                 year -= 1;
 146         }
 147
 148         return (((
 149                 (unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) +
 150                         year*365 - 719499
 151             )*24 + hour /* now have hours */
 152           )*60 + min /* now have minutes */
 153         )*60 + sec; /* finally seconds */
 154 }
 155
 156 #endif