c# 根据日期 获取今天星期几

/// <summary>
/// 根据年月日计算星期几(Label2.Text=CaculateWeekDay(2004,12,9);)
/// </summary>
/// <param name="y">年</param>
/// <param name="m">月</param>
/// <param name="d">日</param>
/// <returns></returns>
public  string CaculateWeekDay(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;
string weekstr = "";
switch (week)
{
case 1: weekstr = "星期一"; break;
case 2: weekstr = "星期二"; break;
case 3: weekstr = "星期三"; break;
case 4: weekstr = "星期四"; break;
case 5: weekstr = "星期五"; break;
case 6: weekstr = "星期六"; break;
case 7: weekstr = "星期日"; break;
}

return weekstr;
}