System.DateTime.AddHours Method

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


public DateTime AddHours (double value)


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


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


ArgumentOutOfRangeExceptionThe resulting DateTime is less than DateTime.MinValue or greater than DateTime.MaxValue.


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

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 DateTime.Add(TimeSpan) 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.


Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0,,