Add and Subtract Dates using DATEADD in SQL Server

Below are examples of using the DATEADD function.  
For all of these examples, the parameter @Date = "2011-09-23 15:48:39.2370000".

Examples of Using the DATEADD Function
Unit of time	Query	Result
NANOSECOND	SELECT DATEADD(NANOSECOND,150000,@Date)	2011-09-23 15:48:39.2371500
MICROSECOND	SELECT DATEADD(MICROSECOND,150000,@Date)	2011-09-23 15:48:39.3870000
MILLISECOND	SELECT DATEADD(MILLISECOND,1500,@Date)	2011-09-23 15:48:39.2385000
SECOND	SELECT DATEADD(SECOND,1500,@Date)	2011-09-23 16:13:39
MINUTE	SELECT DATEADD(MINUTE,15,@Date)	2011-09-23 16:03:39
HOUR	SELECT DATEADD(HOUR,-3,@Date)	2011-09-23 12:48:39
WEEKDAY	SELECT DATEADD(WEEKDAY,-2,@Date)	2011-09-21 15:48:39
WEEK	SELECT DATEADD(WEEK,4,@Date)	2011-10-21 15:48:39
DAY	SELECT DATEADD(DD,4,@Date)	2011-09-27 15:48:39
DAYOFYEAR	SELECT DATEADD(DY,14,@Date)	2011-10-07 15:48:39
MONTH	SELECT DATEADD(MM,-4,@Date)	2011-05-23 15:48:39
QUARTER	SELECT DATEADD(Q,-2,@Date)	2011-03-23 15:48:39
YEAR	SELECT DATEADD(YYYY,-5,@Date)	2006-09-23 15:48:39