1 /*
2 * linux/kernel/mktime.c
3 *
4 * (C) 1991 Linus Torvalds
5 */
6
7 #include <time.h>
8
9 /*
10 * This isn't the library routine, it is only used in the kernel.
11 * as such, we don't care about years<1970 etc, but assume everything
12 * is ok. Similarly, TZ etc is happily ignored. We just do everything
13 * as easily as possible. Let's find something public for the library
14 * routines (although I think minix times is public).
15 */
16 /*
17 * PS. I hate whoever though up the year 1970 - couldn't they have gotten
18 * a leap-year instead? I also hate Gregorius, pope or no. I'm grumpy.
19 */
20 #define MINUTE 60
21 #define HOUR (60*MINUTE)
22 #define DAY (24*HOUR)
23 #define YEAR (365*DAY)
24
25 /* interestingly, we assume leap-years */
26 static int month[12] = {
27 0,
28 DAY*(31),
29 DAY*(31+29),
30 DAY*(31+29+31),
31 DAY*(31+29+31+30),
32 DAY*(31+29+31+30+31),
33 DAY*(31+29+31+30+31+30),
34 DAY*(31+29+31+30+31+30+31),
35 DAY*(31+29+31+30+31+30+31+31),
36 DAY*(31+29+31+30+31+30+31+31+30),
37 DAY*(31+29+31+30+31+30+31+31+30+31),
38 DAY*(31+29+31+30+31+30+31+31+30+31+30)
39 };
40
41 long kernel_mktime(struct tm * tm)
42 {
43 long res;
44 int year;
45
46 year = tm->tm_year - 70;
47 /* magic offsets (y+1) needed to get leapyears right.*/
48 res = YEAR*year + DAY*((year+1)/4);
49 res += month[tm->tm_mon];
50 /* and (y+2) here. If it wasn't a leap-year, we have to adjust */
51 if (tm->tm_mon>1 && ((year+2)%4))
52 res -= DAY;
53 res += DAY*(tm->tm_mday-1);
54 res += HOUR*tm->tm_hour;
55 res += MINUTE*tm->tm_min;
56 res += tm->tm_sec;
57 return res;
58 }
59
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