3 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5 * SPDX-License-Identifier: GPL-2.0+
9 * Date & Time support for Philips PCF8563 RTC
17 #if defined(CONFIG_CMD_DATE) || defined(CONFIG_TIMESTAMP)
20 #define STARTOFTIME 1970
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])
27 static int month_days[12] = {
28 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
32 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
34 int rtc_calc_weekday(struct rtc_time *tm)
39 int MonthOffset[] = { 0,31,59,90,120,151,181,212,243,273,304,334 };
41 if (tm->tm_year < 1753)
43 lastYear=tm->tm_year-1;
46 * Number of leap corrections to apply up to end of last year
48 leapsToDate = lastYear/4 - lastYear/100 + lastYear/400;
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
54 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 will be
56 if((tm->tm_year%4==0) &&
57 ((tm->tm_year%100!=0) || (tm->tm_year%400==0)) &&
60 * We are past Feb. 29 in a leap year
67 day += lastYear*365 + leapsToDate + MonthOffset[tm->tm_mon-1] + tm->tm_mday;
74 void to_tm(int tim, struct rtc_time * tm)
77 register long hms, day;
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;
87 /* Number of years in days */
88 for (i = STARTOFTIME; day >= days_in_year(i); i++) {
89 day -= days_in_year(i);
93 /* Number of months in days left */
94 if (leapyear(tm->tm_year)) {
95 days_in_month(FEBRUARY) = 29;
97 for (i = 1; day >= days_in_month(i); i++) {
98 day -= days_in_month(i);
100 days_in_month(FEBRUARY) = 28;
103 /* Days are what is left over (+1) from all that. */
104 tm->tm_mday = day + 1;
107 * Determine the day of week
109 rtc_calc_weekday(tm);
112 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
113 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
114 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
116 * [For the Julian calendar (which was used in Russia before 1917,
117 * Britain & colonies before 1752, anywhere else before 1582,
118 * and is still in use by some communities) leave out the
119 * -year/100+year/400 terms, and add 10.]
121 * This algorithm was first published by Gauss (I think).
123 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
124 * machines were long is 32-bit! (However, as time_t is signed, we
125 * will already get problems at other places on 2038-01-19 03:14:08)
128 mktime (unsigned int year, unsigned int mon,
129 unsigned int day, unsigned int hour,
130 unsigned int min, unsigned int sec)
132 if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */
133 mon += 12; /* Puts Feb last since it has leap day */
138 (unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) +
140 )*24 + hour /* now have hours */
141 )*60 + min /* now have minutes */
142 )*60 + sec; /* finally seconds */