declare @dd datetime = '1947-2-24'
select datediff(month, @dd, CURRENT_TIMESTAMP)/12

declare @dd datetime = '1947-2-24'
select datediff(month, @dd, CURRENT_TIMESTAMP)/12

DECLARE @DOB DATETIME
SET @DOB = '2008-12-31'
DECLARE @Now DATETIME
SET @Now = '2009-12-30'

select datediff(month, @DOB, @Now)/12

select	a.DOB,
	b.CurrDate,
	BirthdayCurrentYear =
	dateadd(yy,datediff(yy,a.DOB,b.CurrDate),a.DOB),
	Age =
	datediff(yy,a.DOB,b.CurrDate) +
	-- Subtract 1 if current date before birthday in current year
	case when b.CurrDate < dateadd(yy,datediff(yy,a.DOB,b.CurrDate),a.DOB)
	then -1 else 0 end		
from
	( --Test Date of Birth
	select DOB = convert(date,'19600229')	union all
	select DOB = convert(date,'19521013')
	) a	join
	( -- Test Current Dates
	select CurrDate = convert(date,'20110227')	union all
	select CurrDate = convert(date,'20110228')	union all
	select CurrDate = convert(date,'20120228')	union all
	select CurrDate = convert(date,'20120229')	union all
	select CurrDate = convert(date,'20121012')	union all
	select CurrDate = convert(date,'20121013')
	) b	on month(a.DOB) = month(b.CurrDate)
order by
	a.DOB,
	b.CurrDate

DOB        CurrDate   BirthdayCurrentYear Age
---------- ---------- ------------------- -----------
1952-10-13 2012-10-12 2012-10-13          59
1952-10-13 2012-10-13 2012-10-13          60
1960-02-29 2011-02-27 2011-02-28          50
1960-02-29 2011-02-28 2011-02-28          51
1960-02-29 2012-02-28 2012-02-29          51
1960-02-29 2012-02-29 2012-02-29          52