DateTime myValue = DateTime.Now;//系统当前时间2012/5/22 16:47:40  
        String temp = myValue.ToString();//字符接收当前时间"2012/5/22 16:47:40"  
        String temp1 = myValue.ToShortDateString();//"2012/5/22"  
        String temp2 = myValue.ToShortTimeString();//"17:00"  
        String temp3 = myValue.ToLongDateString();//"2012年5月22日"  
 
        String temp4 = myValue.AddDays(3).ToShortDateString();//"2012/5/25"  
        String temp5 = myValue.AddHours(3).ToShortTimeString();//"20:00"  
        String temp6 = myValue.AddDays(-3).ToShortDateString();//"2012/5/19"  
 
        String temp7 = myValue.Month.ToString();//"5"  
        int temp8 = myValue.DayOfYear;//143  
 
        DateTime mybirthday = new DateTime(1987, 12, 15);//{1987/12/15 0:00:00}  
        DateTime mybirthday1 = DateTime.Parse("1987-12-15");//{1987/12/15 0:00:00}  
 
//TimeSpan是一种时间段类型  
          TimeSpan myDays = DateTime.Now.Subtract(mybirthday);//{8925.17:02:07.4040000}  
int mydays=myDays.Days;//8925 

摘自 whuarui2010的专栏