根据年月日算出当前日期是星期几

   /// <summary>
        /// 根据年月日计算星期几
        /// </summary>
        /// <param name="y">年</param>
        /// <param name="m">月</param>
        /// <param name="d">日</param>
        /// <returns></returns>
        public static 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;
            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 0: weekstr = "星期日"; break;
            }

            return weekstr;
        }