ref: e43e3872b43d9c1b49e9e5c015b32258c3735ad8
dir: /src/libc/time/_daysyear.c/
int _daysmon[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int
_daysyear(int year)
{
if (year%4 != 0)
return 365;
if (year%100 == 0 && year%400 != 0)
return 365;
return 366;
}