根据日期，获得星期几

/// <summary>根据日期，获得星期几</summary>
/// <param name="y">年</param> 
/// <param name="m">月</param> 
/// <param name="d">日</param> 
/// <returns>星期几，1代表星期一；7代表星期日</returns>
public static int getWeekDay(int y,int m, int d)
{
    if(m==1) m=13;
    if(m==2) m=14;
    int week=(d+2*m+3*(m+1)/5+y+y/4-y/100+y/400)%7+1;
    return week;
}