date.c
3.49 KB
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/*
* (C) Copyright 2001
* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <common.h>
#include <command.h>
#include <errno.h>
#include <rtc.h>
#if defined(CONFIG_CMD_DATE) || defined(CONFIG_TIMESTAMP)
#define FEBRUARY 2
#define STARTOFTIME 1970
#define SECDAY 86400L
#define SECYR (SECDAY * 365)
#define leapyear(year) ((year) % 4 == 0)
#define days_in_year(a) (leapyear(a) ? 366 : 365)
#define days_in_month(a) (month_days[(a) - 1])
static int month_days[12] = {
31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};
static int month_offset[] = {
0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
};
/*
* This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
*/
int rtc_calc_weekday(struct rtc_time *tm)
{
int leaps_to_date;
int last_year;
int day;
if (tm->tm_year < 1753)
return -1;
last_year = tm->tm_year - 1;
/* Number of leap corrections to apply up to end of last year */
leaps_to_date = last_year / 4 - last_year / 100 + last_year / 400;
/*
* This year is a leap year if it is divisible by 4 except when it is
* divisible by 100 unless it is divisible by 400
*
* e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 is.
*/
if (tm->tm_year % 4 == 0 &&
((tm->tm_year % 100 != 0) || (tm->tm_year % 400 == 0)) &&
tm->tm_mon > 2) {
/* We are past Feb. 29 in a leap year */
day = 1;
} else {
day = 0;
}
day += last_year * 365 + leaps_to_date + month_offset[tm->tm_mon - 1] +
tm->tm_mday;
tm->tm_wday = day % 7;
return 0;
}
int rtc_to_tm(int tim, struct rtc_time *tm)
{
register int i;
register long hms, day;
day = tim / SECDAY;
hms = tim % SECDAY;
/* Hours, minutes, seconds are easy */
tm->tm_hour = hms / 3600;
tm->tm_min = (hms % 3600) / 60;
tm->tm_sec = (hms % 3600) % 60;
/* Number of years in days */
for (i = STARTOFTIME; day >= days_in_year(i); i++)
day -= days_in_year(i);
tm->tm_year = i;
/* Number of months in days left */
if (leapyear(tm->tm_year))
days_in_month(FEBRUARY) = 29;
for (i = 1; day >= days_in_month(i); i++)
day -= days_in_month(i);
days_in_month(FEBRUARY) = 28;
tm->tm_mon = i;
/* Days are what is left over (+1) from all that */
tm->tm_mday = day + 1;
/* Zero unused fields */
tm->tm_yday = 0;
tm->tm_isdst = 0;
/*
* Determine the day of week
*/
return rtc_calc_weekday(tm);
}
/*
* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
* Assumes input in normal date format, i.e. 1980-12-31 23:59:59
* => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
*
* [For the Julian calendar (which was used in Russia before 1917,
* Britain & colonies before 1752, anywhere else before 1582,
* and is still in use by some communities) leave out the
* -year / 100 + year / 400 terms, and add 10.]
*
* This algorithm was first published by Gauss (I think).
*
* WARNING: this function will overflow on 2106-02-07 06:28:16 on
* machines where long is 32-bit! (However, as time_t is signed, we
* will already get problems at other places on 2038-01-19 03:14:08)
*/
unsigned long rtc_mktime(const struct rtc_time *tm)
{
int mon = tm->tm_mon;
int year = tm->tm_year;
int days, hours;
mon -= 2;
if (0 >= (int)mon) { /* 1..12 -> 11, 12, 1..10 */
mon += 12; /* Puts Feb last since it has leap day */
year -= 1;
}
days = (unsigned long)(year / 4 - year / 100 + year / 400 +
367 * mon / 12 + tm->tm_mday) +
year * 365 - 719499;
hours = days * 24 + tm->tm_hour;
return (hours * 60 + tm->tm_min) * 60 + tm->tm_sec;
}
#endif