DateTime.AddDays Method (Double)


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

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

public DateTime AddDays(
	double value


Type: System.Double

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

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 days represented by value.

Exception Condition

The resulting DateTime is less than MinValue or greater than 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 fractional part of valueis the fractional part of a day. For example, 4.5 is equivalent to 4 days, 12 hours, 0 minutes, 0 seconds, 0 milliseconds, and 0 ticks.

The value parameter is rounded to the nearest millisecond.

TheAddDays method takes into account leap years and the number of days in a month when performing date arithmetic.

The following example uses the AddDays method to determine the day of the week 36 days after the current date.

using System;

class Class1
	static void Main()
		DateTime today = DateTime.Now;
		DateTime answer = today.AddDays(36);
        Console.WriteLine("Today: {0:dddd}", today);
        Console.WriteLine("36 days from today: {0:dddd}", answer);
// The example displays output like the following:
//       Today: Wednesday
//       36 days from today: Thursday

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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