Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

DateTime.AddHours Method

Updated: September 2008

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

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

public DateTime AddHours(
	double value
)

Parameters

value
Type: System.Double

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

Return Value

Type: System.DateTime
A DateTime 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 less than DateTime.MinValue or greater than DateTime.MaxValue.

This method does not change the value of this DateTime object. Instead, a new DateTime object 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.

using System;

public class Example
{
   public static void Main()
   {
      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)
         Console.WriteLine("{0} + {1} hour(s) = {2}", 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

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

September 2008

Added details to the Remarks and an example.

Customer feedback.

Community Additions

Show:
© 2014 Microsoft