ref: ee0956cca3f5a2e8ea346336086e37296b3767d9
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;
}