SQL DATEADD Function

Returns a new datetime value based on adding an interval to the specified date.
SQL DATEADD SyntaxDATEADD ( datepart , number, date )


DECLARE @DateNow DATETIME
SET @DateNow='2007-06-04'
SELECT DATEADD(Year, 3, @DateNow) AS NewDate 
Return Value = 2010-06-04 00:00:00.000

SELECT DATEADD(quarter, 3, @DateNow) AS NewDate
Return Value = 2008-03-04 00:00:00.000

SELECT DATEADD(Month, 3, @DateNow) AS NewDate
Return Value = 2007-09-04 00:00:00.000

SELECT DATEADD(dayofyear,3, @DateNow) AS NewDate
Return Value = 2007-06-07 00:00:00.000

SELECT DATEADD(Day, 3, @DateNow) AS NewDate
Return Value = 2007-06-07 00:00:00.000

SELECT DATEADD(Week, 3, @DateNow) AS NewDateReturn Value = 2007-06-25 00:00:00.000


SELECT DATEADD(Hour, 3, @DateNow) AS NewDate
Return Value = 2007-06-04 03:00:00.000

SELECT DATEADD(minute, 3, @DateNow) AS NewDate
Return Value = 2007-06-04 00:03:00.000

SELECT DATEADD(second, 3, @DateNow) AS NewDate
Return Value = 2007-06-04 00:00:03.000

SELECT DATEADD(millisecond, 3, @DateNow) AS NewDate
Return Value = 2007-06-04 00:00:00.003




repost from : http://sqltutorials.blogspot.com/2007/06/sql-dateadd-function.html