C# 時間計算 今天、昨天、前天、明天 一個月的開始日期與結束日期

C# 時間計算

 

 今天、昨天、前天、明天

  class Program
    {
        static void Main(string[] args)
        {
            DateTime dt1=GetTodayZeroTime(DateTime.Now);
            Console.WriteLine("今天零點：{0}",dt1.ToString() );
            DateTime dt2 = GetYestodayZeroTime(DateTime.Now);
            Console.WriteLine("昨天零點：{0}", dt2.ToString());
            DateTime dt3 = GetDayBeforYestodayZeroTime(DateTime.Now);
            Console.WriteLine("前天零點：{0}", dt3.ToString());
            DateTime dt4 = GetTomorrowZeroTime(DateTime.Now);
            Console.WriteLine("明天零點：{0}", dt4.ToString());
            Console.ReadLine();

        }

        private static DateTime GetTodayZeroTime(DateTime datetime)
        {
            return new DateTime(datetime.Year, datetime.Month, datetime.Day);
        }

        private static DateTime GetYestodayZeroTime(DateTime datetime)
        {
            TimeSpan timespan = new TimeSpan(1, 0, 0, 0);
            DateTime yesdt = datetime.Subtract(timespan);
            return new DateTime(yesdt.Year, yesdt.Month, yesdt.Day);
        }

        private static DateTime GetDayBeforYestodayZeroTime(DateTime datetime)
        {
            TimeSpan timespan = new TimeSpan(2, 0, 0, 0);
            DateTime yesdt = datetime.Subtract(timespan);
            return new DateTime(yesdt.Year, yesdt.Month, yesdt.Day);
        }

        private static DateTime GetTomorrowZeroTime(DateTime datetime)
        {
            TimeSpan timespan = new TimeSpan(1, 0, 0, 0);
            DateTime yesdt = datetime.Add(timespan);
            return new DateTime(yesdt.Year, yesdt.Month, yesdt.Day);
        }
    }

 

 

C# 取某一天所在周的最后一天，所在月的最后一天

本文來自網絡上朋友們的帖子，這里進行了一個匯總

取一個月的最后一天日期

int   yy   =   2005; 
int   mm   =   11; 
int   Lastday   =   DateTime.DaysInMonth(yy,   mm);  

另一種方法

int   year   =   2005; 
int   month   =   11; 
DateTime   dt   =   new   DateTime(year,month,1).AddMonths(1).AddDays(-1);

取某一天所在周的最后一天日期

String   date   =   "2007-09-27 "; 
SimpleDateFormat   sdf   =   new   SimpleDateFormat( "yyyy-MM-dd "); 
Calendar   calendar   =   new   GregorianCalendar(); 
calendar.setTime(sdf.parse(date)); 
calendar.set(Calendar.DAY_OF_WEEK,   calendar.getMaximum(Calendar.DAY_OF_WEEK)); 
System.out.println(sdf.format(calendar.getTime())); 

 

時間比較：

 

DateTime date1 =  new DateTime(2009, 8, 1, 0, 0, 0);
DateTime date2 =  new DateTime(2009, 8, 1, 12, 0, 0);
int result = DateTime.Compare(date1, date2);
string relationship;

if (result < 0)
   relationship =  "is earlier than";
else  if (result == 0)
   relationship =  "is the same time as";         
else
   relationship =  "is later than";

Console.WriteLine( "{0} {1} {2}", date1, relationship, date2);
// The example displays the following output:
//    8/1/2009 12:00:00 AM is earlier than 8/1/2009 12:00:00 PM

時間比較：
    while (DateTime.Compare(dtBegin, dtEnd) <= 0)
            {
                // 

                //循環主體

                 //    

                dtBegin = dtBegin.AddHours(1);           //時間相加
            }

 時間相減：

  TimeSpan ts = endtime.Subtract(begintime).Duration();