DateTime.AddDays Method

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 Function AddDays ( _
    value As Double _
) As DateTime
public DateTime AddDays(
    double value


  • value
    Type: System.Double
    The number of whole and fractional days 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 days represented by value.


Exception Condition

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 fractional part of value is 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.


The following example demonstrates the AddDays method.

' Calculate what day of the week is 36 days from this instant.
Dim today As System.DateTime
Dim answer As System.DateTime

today = System.DateTime.Now
answer = today.AddDays(36)

outputBlock.Text += String.Format("{0:dddd}", answer) + vbCrLf
// Calculate what day of the week is 36 days from this instant.
System.DateTime today = System.DateTime.Now;
System.DateTime answer = today.AddDays(36);
outputBlock.Text += String.Format("{0:dddd}", answer) + "\n";

Version Information


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


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