计算星期几

date: 2015-11-17 11:55:58

int dayofweek(int y, int m, int d)    /* 0 = Sunday */
{
    static int t[] = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
    y -= m < 3;
    return (y + y/4 - y/100 + y/400 + t[m-1] + d) % 7;
}