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DateTimeOffset.AddHours Method

Adds a specified number of whole and fractional hours to the current DateTimeOffset object.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

public DateTimeOffset AddHours(
	double hours


Type: System.Double

A number of whole and fractional hours. The number can be negative or positive.

Return Value

Type: System.DateTimeOffset
A DateTimeOffset object whose value is the sum of the date and time represented by the current DateTimeOffset object and the number of hours represented by hours.


The resulting DateTimeOffset value is less than MinValue.


The resulting DateTimeOffset value is greater than MaxValue.

The fractional part of the hours parameter is the fractional part of an hour. For example, 4.5 is equivalent to 4 hours, 30 minutes, 0 seconds, 0 milliseconds. The hours parameter is rounded to the nearest millisecond.


This method returns a new DateTimeOffset object. It does not modify the value of the current object by adding hours to its date and time.

Because a DateTimeOffset object does not represent the date and time in a specific time zone, the AddHours method does not consider a particular time zone's adjustment rules when it performs date and time arithmetic.

Converting time intervals of less than an hour to a fraction can involve a loss of precision. (For example, one minute is 0.01666 of an hour.) If this is problematic, you can use the Add method, which enables you to specify more than one kind of time interval in a single method call and eliminates the need to convert time intervals to fractional parts of an hour.

The following example uses the AddHours method to list the start times of work shifts for a particular week at an office that has two eight-hour shifts per day.

const int SHIFT_LENGTH = 8;

DateTimeOffset startTime = new DateTimeOffset(2007, 8, 6, 0, 0, 0, 
DateTimeOffset startOfShift = startTime.AddHours(SHIFT_LENGTH);

Console.WriteLine("Shifts for the week of {0:D}", startOfShift);
   // Exclude third shift 
   if (startOfShift.Hour > 6)
      Console.WriteLine("   {0:d} at {0:T}", startOfShift);

   startOfShift = startOfShift.AddHours(SHIFT_LENGTH);
} while (startOfShift.DayOfWeek != DayOfWeek.Saturday &
           startOfShift.DayOfWeek != DayOfWeek.Sunday);
// The example produces the following output: 
//    Shifts for the week of Monday, August 06, 2007 
//       8/6/2007 at 8:00:00 AM 
//       8/6/2007 at 4:00:00 PM 
//       8/7/2007 at 8:00:00 AM 
//       8/7/2007 at 4:00:00 PM 
//       8/8/2007 at 8:00:00 AM 
//       8/8/2007 at 4:00:00 PM 
//       8/9/2007 at 8:00:00 AM 
//       8/9/2007 at 4:00:00 PM 
//       8/10/2007 at 8:00:00 AM 
//       8/10/2007 at 4:00:00 PM                 

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5 SP1, 3.0 SP1, 2.0 SP1