If a person's DOB = '1988-02-24 15:00:00.000', the age should be 20 already as of today (March 5th, 2008).

But the 3rd query returns 19.

select DATEDIFF(yy, '1988-02-24 15:00:00.000', GETDATE()) - CASE WHEN DATEPART(m, '1988-02-24 15:00:00.000') >= DATEPART(m, GETDATE()) AND DATEPART(d, '1988-02-24 15:00:00.000') >= DATEPART(d, GETDATE()) THEN 0 ELSE 1 END

Does the 3rd query return the right age?