User DATEADD(datepart,number,date) function
Where date is a valid date expression and number is the number of interval you want to add. The number can either be positive, for dates in the future, or negative, for dates in the past.
datepart can be one of the following:
datepart Abbreviation
year yy, yyyy
quarter qq, q
month mm, m
dayofyear dy, y
day dd, d
week wk, ww
weekday dw, w
hour hh
minute mi, n
second ss, s
millisecond ms
microsecond mcs
nanosecond ns
eg: DATEADD(year,60,DOB)