根据日期计算某个月有多少天

// 根据日期计算某个月有多少天
static int DaysOfMonth(int year, int month)
{
	static const char sDays[2][12] = {
		31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 
			31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
	};
	
	if (month < 1) {
		month += 12;
		year--;
	}
	else if (month > 12) {
		month -= 12;
		year++;
	}
	
	return sDays[(year % 100 != 0 && year % 4 == 0) || year % 400 == 0][month - 1];
}