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 #include <common.h> 9 #include <command.h> 10 #include <errno.h> 11 #include <rtc.h> 12 13 #if defined(CONFIG_CMD_DATE) || defined(CONFIG_TIMESTAMP) 14 15 #define FEBRUARY 2 16 #define STARTOFTIME 1970 17 #define SECDAY 86400L 18 #define SECYR (SECDAY * 365) 19 #define leapyear(year) ((year) % 4 == 0) 20 #define days_in_year(a) (leapyear(a) ? 366 : 365) 21 #define days_in_month(a) (month_days[(a) - 1]) 22 23 static int month_days[12] = { 24 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 25 }; 26 27 static int month_offset[] = { 28 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 29 }; 30 31 /* 32 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK) 33 */ 34 int rtc_calc_weekday(struct rtc_time *tm) 35 { 36 int leaps_to_date; 37 int last_year; 38 int day; 39 40 if (tm->tm_year < 1753) 41 return -1; 42 last_year = tm->tm_year - 1; 43 44 /* Number of leap corrections to apply up to end of last year */ 45 leaps_to_date = last_year / 4 - last_year / 100 + last_year / 400; 46 47 /* 48 * This year is a leap year if it is divisible by 4 except when it is 49 * divisible by 100 unless it is divisible by 400 50 * 51 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 is. 52 */ 53 if (tm->tm_year % 4 == 0 && 54 ((tm->tm_year % 100 != 0) || (tm->tm_year % 400 == 0)) && 55 tm->tm_mon > 2) { 56 /* We are past Feb. 29 in a leap year */ 57 day = 1; 58 } else { 59 day = 0; 60 } 61 62 day += last_year * 365 + leaps_to_date + month_offset[tm->tm_mon - 1] + 63 tm->tm_mday; 64 tm->tm_wday = day % 7; 65 66 return 0; 67 } 68 69 int rtc_to_tm(int tim, struct rtc_time *tm) 70 { 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 tm->tm_year = i; 86 87 /* Number of months in days left */ 88 if (leapyear(tm->tm_year)) 89 days_in_month(FEBRUARY) = 29; 90 for (i = 1; day >= days_in_month(i); i++) 91 day -= days_in_month(i); 92 days_in_month(FEBRUARY) = 28; 93 tm->tm_mon = i; 94 95 /* Days are what is left over (+1) from all that */ 96 tm->tm_mday = day + 1; 97 98 /* Zero unused fields */ 99 tm->tm_yday = 0; 100 tm->tm_isdst = 0; 101 102 /* 103 * Determine the day of week 104 */ 105 return rtc_calc_weekday(tm); 106 } 107 108 /* 109 * Converts Gregorian date to seconds since 1970-01-01 00:00:00. 110 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 111 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59. 112 * 113 * [For the Julian calendar (which was used in Russia before 1917, 114 * Britain & colonies before 1752, anywhere else before 1582, 115 * and is still in use by some communities) leave out the 116 * -year / 100 + year / 400 terms, and add 10.] 117 * 118 * This algorithm was first published by Gauss (I think). 119 * 120 * WARNING: this function will overflow on 2106-02-07 06:28:16 on 121 * machines where long is 32-bit! (However, as time_t is signed, we 122 * will already get problems at other places on 2038-01-19 03:14:08) 123 */ 124 unsigned long rtc_mktime(const struct rtc_time *tm) 125 { 126 int mon = tm->tm_mon; 127 int year = tm->tm_year; 128 int days, hours; 129 130 mon -= 2; 131 if (0 >= (int)mon) { /* 1..12 -> 11, 12, 1..10 */ 132 mon += 12; /* Puts Feb last since it has leap day */ 133 year -= 1; 134 } 135 136 days = (unsigned long)(year / 4 - year / 100 + year / 400 + 137 367 * mon / 12 + tm->tm_mday) + 138 year * 365 - 719499; 139 hours = days * 24 + tm->tm_hour; 140 return (hours * 60 + tm->tm_min) * 60 + tm->tm_sec; 141 } 142 143 #endif 144