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