1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * (C) Copyright 2001
4 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
5 */
6
7 #include <command.h>
8 #include <errno.h>
9 #include <rtc.h>
10 #include <linux/time.h>
11
12 #define FEBRUARY 2
13 #define STARTOFTIME 1970
14 #define SECDAY 86400L
15 #define SECYR (SECDAY * 365)
16 #define leapyear(year) ((year) % 4 == 0)
17 #define days_in_year(a) (leapyear(a) ? 366 : 365)
18 #define days_in_month(a) (month_days[(a) - 1])
19
20 static int month_offset[] = {
21 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
22 };
23
24 /*
25 * This only works for the Gregorian calendar - i.e. after 1752 (in the UK)
26 */
rtc_calc_weekday(struct rtc_time * tm)27 int rtc_calc_weekday(struct rtc_time *tm)
28 {
29 int leaps_to_date;
30 int last_year;
31 int day;
32
33 if (tm->tm_year < 1753)
34 return -1;
35 last_year = tm->tm_year - 1;
36
37 /* Number of leap corrections to apply up to end of last year */
38 leaps_to_date = last_year / 4 - last_year / 100 + last_year / 400;
39
40 /*
41 * This year is a leap year if it is divisible by 4 except when it is
42 * divisible by 100 unless it is divisible by 400
43 *
44 * e.g. 1904 was a leap year, 1900 was not, 1996 is, and 2000 is.
45 */
46 if (tm->tm_year % 4 == 0 &&
47 ((tm->tm_year % 100 != 0) || (tm->tm_year % 400 == 0)) &&
48 tm->tm_mon > 2) {
49 /* We are past Feb. 29 in a leap year */
50 day = 1;
51 } else {
52 day = 0;
53 }
54
55 day += last_year * 365 + leaps_to_date + month_offset[tm->tm_mon - 1] +
56 tm->tm_mday;
57 tm->tm_wday = day % 7;
58
59 return 0;
60 }
61
62 /*
63 * Converts Gregorian date to seconds since 1970-01-01 00:00:00.
64 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
65 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
66 *
67 * [For the Julian calendar (which was used in Russia before 1917,
68 * Britain & colonies before 1752, anywhere else before 1582,
69 * and is still in use by some communities) leave out the
70 * -year / 100 + year / 400 terms, and add 10.]
71 *
72 * This algorithm was first published by Gauss (I think).
73 */
rtc_mktime(const struct rtc_time * tm)74 time64_t rtc_mktime(const struct rtc_time *tm)
75 {
76 int mon = tm->tm_mon;
77 int year = tm->tm_year;
78 unsigned long days;
79 time64_t hours;
80
81 mon -= 2;
82 if (0 >= mon) { /* 1..12 -> 11, 12, 1..10 */
83 mon += 12; /* Puts Feb last since it has leap day */
84 year -= 1;
85 }
86
87 days = (unsigned long)(year / 4 - year / 100 + year / 400 +
88 367 * mon / 12 + tm->tm_mday) +
89 year * 365 - 719499;
90 hours = days * 24 + tm->tm_hour;
91 return (hours * 60 + tm->tm_min) * 60 + tm->tm_sec;
92 }
93
94 /* for compatibility with linux code */
mktime64(const unsigned int year,const unsigned int mon,const unsigned int day,const unsigned int hour,const unsigned int min,const unsigned int sec)95 time64_t mktime64(const unsigned int year, const unsigned int mon,
96 const unsigned int day, const unsigned int hour,
97 const unsigned int min, const unsigned int sec)
98 {
99 struct rtc_time time;
100
101 time.tm_year = year;
102 time.tm_mon = mon;
103 time.tm_mday = day;
104 time.tm_hour = hour;
105 time.tm_min = min;
106 time.tm_sec = sec;
107
108 return rtc_mktime((const struct rtc_time *)&time);
109 }
110