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 <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 */
rtc_calc_weekday(struct rtc_time * tm)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
rtc_to_tm(int tim,struct rtc_time * tm)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 */
rtc_mktime(const struct rtc_time * tm)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