DATEADD
This function adds a specified number value (signed integer) to a specified datepart of an input date value, depending on the INTERVAL specified and then returns the modified value.
Syntax
DATEADD (INTERVAL, value, datepart )
Example
SELECT 'day',DATEADD(DAY,1,’2007-03-01 11:15:9.23’)
returns
day 2007-03-02 11:15:9.23