Depends on how you define a quarter, and the form that you are looking for
(i.e. 1Q09, 1Q2009, among others).
If you mean a calendar quarter and the date is A1, then try one of the
following:
=ROUNDUP(MONTH(A1)/3,0) & "Q" & YEAR(A1)
=ROUNDUP(MONTH(A1)/3,0) & "Q" & RIGHT(YEAR(A1),2)
Format with right Horizontal Alignment, if that's what you want.