Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
DateAdd Method (String, Double, Object)
Collapse the table of content
Expand the table of content

DateAndTime.DateAdd Method (String, Double, Object)

Returns a Date value containing a date and time value to which a specified time interval has been added.

Namespace:  Microsoft.VisualBasic
Assembly:  Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)

public static DateTime DateAdd(
	string Interval,
	double Number,
	Object DateValue


Type: System.String

Required. DateInterval enumeration value or String expression representing the time interval you want to add.

Type: System.Double

Required. Double. Floating-point expression representing the number of intervals you want to add. Number can be positive (to get date/time values in the future) or negative (to get date/time values in the past). It can contain a fractional part when Interval specifies hours, minutes, or seconds. For other values of Interval, any fractional part of Number is ignored.

Type: System.Object

Required. Date. An expression representing the date and time to which the interval is to be added. DateValue itself is not changed in the calling program.

Return Value

Type: System.DateTime
Returns a Date value containing a date and time value to which a specified time interval has been added.


DateValue is not coercible to Date.


Interval is not valid.


Calculated date is before 00:00:00 on January 1 of the year 1, or later than 23:59:59 on December 31, 9999.

You can use the DateAdd function to add or subtract a specified time interval from a date. For example, you can calculate a date 30 days from today or a time 45 minutes before now.

To add days to DateValue, you can use DateInterval.Day, DateInterval.DayOfYear, or DateInterval.Weekday. These are treated as equivalent because DayOfYear and Weekday are not meaningful time intervals.

The DateAdd function never returns an invalid date. If necessary, the day part of the resulting date is adjusted downward to the last day of the resulting month in the resulting year. The following example adds one month to January 31:

Dim NextMonth As Date = DateAdd(DateInterval.Month, 1, #1/31/1995#)

In this example, DateAdd returns #2/28/1995#, not #2/31/1995#. If DateValue is #1/31/1996#, it returns #2/29/1996# because 1996 is a leap year.


DateAdd uses the current calendar setting from the CurrentCulture property of the CultureInfo class in the System.Globalization namespace. The default CurrentCulture values are determined by Control Panel settings.

Since every Date value is supported by a DateTime structure, its methods give you additional options in adding time intervals. For example, you can add a fractional number of days, rounded to the nearest millisecond, to a Date variable as follows:

Dim NextTime As Date = Now        ' Current date and time.
NextTime = NextTime.AddDays(3.4)  ' Increment by 3 2/5 days.

The Interval argument can have one of the following settings.

Enumeration value


Unit of time interval to add



Day; truncated to integral value



Day; truncated to integral value



Hour; rounded to nearest millisecond



Minute; rounded to nearest millisecond



Month; truncated to integral value



Quarter; truncated to integral value



Second; rounded to nearest millisecond



Day; truncated to integral value



Week; truncated to integral value



Year; truncated to integral value

This example takes a date and, using the DateAdd function, displays a corresponding date a specified number of months in the future.

Dim dateEntered As String =
InputBox("Enter a date", DefaultResponse:=Date.Now.ToShortDateString)
Dim monthsEntered As String =
InputBox("Enter number of months to add", DefaultResponse:="12")

Dim dateValue As Date = Date.Parse(dateEntered)
Dim monthsValue As Integer = Integer.Parse(monthsEntered)

' Add the months to the date. 
Dim newDate As Date = DateAdd(DateInterval.Month, monthsValue, dateValue)

' This statement has a string interval argument, and 
' is equivalent to the above statement. 
'Dim newDate As Date = DateAdd("m", monthsValue, dateValue)

MessageBox.Show("New date: " & newDate.ToShortDateString)

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
© 2015 Microsoft