src/time/__month_to_secs.c

int __month_to_secs(int month, int is_leap) {
    static const int secs_through_month[] = {0, 31 * 86400, 59 * 86400, 90 * 86400,
                                             120 * 86400, 151 * 86400, 181 * 86400, 212 * 86400,
                                             243 * 86400, 273 * 86400, 304 * 86400, 334 * 86400};
    int t = secs_through_month[month];
    if (is_leap && month >= 2)
        t += 86400;
    return t;
}