isleap_sum
len = isleap_sum(year, base) ?
yday += isleap_sum(year, base) ?
tm->tm_yday = start_of_month[isleap_sum(tm->tm_year,
isleap = isleap_sum(tm->tm_year, TM_YEAR_BASE);
isleap = isleap_sum(tm->tm_year, TM_YEAR_BASE);
result += DAYSPERNYEAR + isleap_sum(tmy, TM_YEAR_BASE);
yday += 365 + isleap_sum(b->tm_year, TM_YEAR_BASE);