Article
11/17/2011

DateTime.AddHours Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Returns a new DateTime that adds the specified number of hours to the value of this instance.

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

Syntax

'Declaration
Public Function AddHours ( _
    value As Double _
) As DateTime

public DateTime AddHours(
    double value
)

Parameters

value
Type: System.Double
The number of whole and fractional hours to add. This value can be positive or negative.

Return Value

Type: System.DateTime
An object whose value is the sum of the date and time represented by this instance and the number of hours represented by value.

Exceptions

Exception	Condition
ArgumentOutOfRangeException	The resulting DateTime is earlier than DateTime.MinValue or later than DateTime.MaxValue.

Remarks

This method does not change the value of this DateTime. Instead, a new DateTime is returned whose value is the result of this operation. The Kind property of the returned DateTime object is the same as that of the original DateTime object.

The fractional part of value is the fractional part of an hour. For example, 4.5 is equivalent to 4 hours, 30 minutes, 0 seconds, 0 milliseconds, and 0 ticks.

The value parameter is rounded to the nearest millisecond.

Converting time intervals of less than an hour to a fraction can involve a loss of precision if the result is a non-terminating repeating decimal. (For example, one minute is 0.016667 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.

Examples

The following example uses the AddHours method to add a number of whole and fractional values to a date and time. It also illustrates the loss of precision caused by passing a value that includes a fractional component to the method.

Module Example
   Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
      Dim hours() As Double = {.08333, .16667, .25, .33333, .5, .66667, 1, 2, _
                             29, 30, 31, 90, 365}
      Dim dateValue As Date = #3/1/2009 12:00#

      For Each hour As Double In hours
         outputBlock.Text += String.Format("{0} + {1} hour(s) = {2}", dateValue, _
                                           hour, dateValue.AddHours(hour)) + vbCrLf
      Next                             
   End Sub
End Module
' The example displays the following output on a system whose current
' culture is en-US:
' 3/1/2009 12:00:00 PM + 0.08333 hour(s) = 3/1/2009 12:04:59 PM
' 3/1/2009 12:00:00 PM + 0.16667 hour(s) = 3/1/2009 12:10:00 PM
' 3/1/2009 12:00:00 PM + 0.25 hour(s) = 3/1/2009 12:15:00 PM
' 3/1/2009 12:00:00 PM + 0.33333 hour(s) = 3/1/2009 12:19:59 PM
' 3/1/2009 12:00:00 PM + 0.5 hour(s) = 3/1/2009 12:30:00 PM
' 3/1/2009 12:00:00 PM + 0.66667 hour(s) = 3/1/2009 12:40:00 PM
' 3/1/2009 12:00:00 PM + 1 hour(s) = 3/1/2009 1:00:00 PM
' 3/1/2009 12:00:00 PM + 2 hour(s) = 3/1/2009 2:00:00 PM
' 3/1/2009 12:00:00 PM + 29 hour(s) = 3/2/2009 5:00:00 PM
' 3/1/2009 12:00:00 PM + 30 hour(s) = 3/2/2009 6:00:00 PM
' 3/1/2009 12:00:00 PM + 31 hour(s) = 3/2/2009 7:00:00 PM
' 3/1/2009 12:00:00 PM + 90 hour(s) = 3/5/2009 6:00:00 AM
' 3/1/2009 12:00:00 PM + 365 hour(s) = 3/16/2009 5:00:00 PM

using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      double[] hours = {.08333, .16667, .25, .33333, .5, .66667, 1, 2, 
                        29, 30, 31, 90, 365};
      DateTime dateValue = new DateTime(2009, 3, 1, 12, 0, 0);

      foreach (double hour in hours)
         outputBlock.Text += String.Format("{0} + {1} hour(s) = {2}\n", dateValue, 
                                           hour, dateValue.AddHours(hour));
   }
}
// The example displays the following output on a system whose current
// culture is en-US:
//    3/1/2009 12:00:00 PM + 0.08333 hour(s) = 3/1/2009 12:04:59 PM
//    3/1/2009 12:00:00 PM + 0.16667 hour(s) = 3/1/2009 12:10:00 PM
//    3/1/2009 12:00:00 PM + 0.25 hour(s) = 3/1/2009 12:15:00 PM
//    3/1/2009 12:00:00 PM + 0.33333 hour(s) = 3/1/2009 12:19:59 PM
//    3/1/2009 12:00:00 PM + 0.5 hour(s) = 3/1/2009 12:30:00 PM
//    3/1/2009 12:00:00 PM + 0.66667 hour(s) = 3/1/2009 12:40:00 PM
//    3/1/2009 12:00:00 PM + 1 hour(s) = 3/1/2009 1:00:00 PM
//    3/1/2009 12:00:00 PM + 2 hour(s) = 3/1/2009 2:00:00 PM
//    3/1/2009 12:00:00 PM + 29 hour(s) = 3/2/2009 5:00:00 PM
//    3/1/2009 12:00:00 PM + 30 hour(s) = 3/2/2009 6:00:00 PM
//    3/1/2009 12:00:00 PM + 31 hour(s) = 3/2/2009 7:00:00 PM
//    3/1/2009 12:00:00 PM + 90 hour(s) = 3/5/2009 6:00:00 AM
//    3/1/2009 12:00:00 PM + 365 hour(s) = 3/16/2009 5:00:00 PM

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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