1long long __year_to_secs(long long year, int *is_leap)
2{
3	if (year-2ULL <= 136) {
4		int y = year;
5		int leaps = (y-68)>>2;
6		if (!((y-68)&3)) {
7			leaps--;
8			if (is_leap) *is_leap = 1;
9		} else if (is_leap) *is_leap = 0;
10		return 31536000*(y-70) + 86400*leaps;
11	}
12
13	int cycles, centuries, leaps, rem;
14
15	if (!is_leap) is_leap = &(int){0};
16	cycles = (year-100) / 400;
17	rem = (year-100) % 400;
18	if (rem < 0) {
19		cycles--;
20		rem += 400;
21	}
22	if (!rem) {
23		*is_leap = 1;
24		centuries = 0;
25		leaps = 0;
26	} else {
27		if (rem >= 200) {
28			if (rem >= 300) centuries = 3, rem -= 300;
29			else centuries = 2, rem -= 200;
30		} else {
31			if (rem >= 100) centuries = 1, rem -= 100;
32			else centuries = 0;
33		}
34		if (!rem) {
35			*is_leap = 0;
36			leaps = 0;
37		} else {
38			leaps = rem / 4U;
39			rem %= 4U;
40			*is_leap = !rem;
41		}
42	}
43
44	leaps += 97*cycles + 24*centuries - *is_leap;
45
46	return (year-100) * 31536000LL + leaps * 86400LL + 946684800 + 86400;
47}
48