leap_days
days -= leap_days(year, new_year);
+ leap_days(1970, result->tm_year)
time_t days = 365 * ((time_t) year - 1970) + leap_days(1970, year);
uint64_t days = 365 * (year - 1970) + leap_days(1970, year);
uint64_t days = 365 * (yr - 1970) + (uint64_t)leap_days((uint32_t)yr);
days -= leap_days(year, new_year);
+ leap_days(1970, result->tm_year)
time_t days = 365 * ((time_t) year - 1970) + leap_days(1970, year);