1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * (C) Copyright 2001 4 * Wolfgang Denk, DENX Software Engineering, wd (at) denx.de. 5 */ 6 7 #include <common.h> 8 #include <command.h> 9 #include <errno.h> 10 #include <rtc.h> 11 12 #if defined(CONFIG_CMD_DATE) || defined(CONFIG_TIMESTAMP) 13 14 #define FEBRUARY 2 15 #define STARTOFTIME 1970 16 #define SECDAY 86400L 17 #define SECYR (SECDAY * 365) 18 #define leapyear(year) ((year) % 4 == 0) 19 #define days_in_year(a) (leapyear(a) ? 366 : 365) 20 #define days_in_month(a) (month_days[(a) - 1]) 21 22 static int month_days[12] = { 23 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 24 }; 25 26 static int month_offset[] = { 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 int rtc_calc_weekday(struct rtc_time *tm) 34 { 35 int leaps_to_date; 36 int last_year; 37 int day; 38 39 if (tm->tm_year < 1753) 40 return -1; 41 last_year = tm->tm_year - 1; 42 43 /* Number of leap corrections to apply up to end of last year */ 44 leaps_to_date = last_year / 4 - last_year / 100 + last_year / 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 is. 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 /* We are past Feb. 29 in a leap year */ 56 day = 1; 57 } else { 58 day = 0; 59 } 60 61 day += last_year * 365 + leaps_to_date + month_offset[tm->tm_mon - 1] + 62 tm->tm_mday; 63 tm->tm_wday = day % 7; 64 65 return 0; 66 } 67 68 int rtc_to_tm(int tim, struct rtc_time *tm) 69 { 70 register int i; 71 register long hms, day; 72 73 day = tim / SECDAY; 74 hms = tim % SECDAY; 75 76 /* Hours, minutes, seconds are easy */ 77 tm->tm_hour = hms / 3600; 78 tm->tm_min = (hms % 3600) / 60; 79 tm->tm_sec = (hms % 3600) % 60; 80 81 /* Number of years in days */ 82 for (i = STARTOFTIME; day >= days_in_year(i); i++) 83 day -= days_in_year(i); 84 tm->tm_year = i; 85 86 /* Number of months in days left */ 87 if (leapyear(tm->tm_year)) 88 days_in_month(FEBRUARY) = 29; 89 for (i = 1; day >= days_in_month(i); i++) 90 day -= days_in_month(i); 91 days_in_month(FEBRUARY) = 28; 92 tm->tm_mon = i; 93 94 /* Days are what is left over (+1) from all that */ 95 tm->tm_mday = day + 1; 96 97 /* Zero unused fields */ 98 tm->tm_yday = 0; 99 tm->tm_isdst = 0; 100 101 /* 102 * Determine the day of week 103 */ 104 return rtc_calc_weekday(tm); 105 } 106 107 /* 108 * Converts Gregorian date to seconds since 1970-01-01 00:00:00. 109 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 110 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59. 111 * 112 * [For the Julian calendar (which was used in Russia before 1917, 113 * Britain & colonies before 1752, anywhere else before 1582, 114 * and is still in use by some communities) leave out the 115 * -year / 100 + year / 400 terms, and add 10.] 116 * 117 * This algorithm was first published by Gauss (I think). 118 * 119 * WARNING: this function will overflow on 2106-02-07 06:28:16 on 120 * machines where long is 32-bit! (However, as time_t is signed, we 121 * will already get problems at other places on 2038-01-19 03:14:08) 122 */ 123 unsigned long rtc_mktime(const struct rtc_time *tm) 124 { 125 int mon = tm->tm_mon; 126 int year = tm->tm_year; 127 int days, hours; 128 129 mon -= 2; 130 if (0 >= (int)mon) { /* 1..12 -> 11, 12, 1..10 */ 131 mon += 12; /* Puts Feb last since it has leap day */ 132 year -= 1; 133 } 134 135 days = (unsigned long)(year / 4 - year / 100 + year / 400 + 136 367 * mon / 12 + tm->tm_mday) + 137 year * 365 - 719499; 138 hours = days * 24 + tm->tm_hour; 139 return (hours * 60 + tm->tm_min) * 60 + tm->tm_sec; 140 } 141 142 #endif 143
