输入日期可以计算星期几

string today = "yourDate";
DateTime day = Convert.ToDateTime(today);
//English
string week = day.DayOfWeek.ToString();
//中文
System.Globalization.CultureInfo cultureInfo = new System.Globalization.CultureInfo("zh-CN");
string week_cn = "星期"+cultureInfo.DateTimeFormat.GetAbbreviatedDayName(day.DayOfWeek).ToString();