DateTime.AddHours Method

July 28, 2014

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

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

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

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.

ExceptionCondition
ArgumentOutOfRangeException

The resulting DateTime is earlier than DateTime.MinValue or later than DateTime.MaxValue.

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.

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


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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