And Lynn's method declares the leap-year person to be 18 on the 28th.

ScottPletcher (3/16/2009)

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Yes, but I think someone made that point that legally in some jurisdictions, a person with a birthday of Feb 29 is legally older on Feb 28. This is inconvenient for IT people, but if it's a legal requirement, we must handle it. :)

David. (8/27/2009)

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This demonstrates that the datediff solution does not change the age at the time of the birthdate. All the age results are the same:
declare @BirthDate DATETIME
set @BirthDate = '08/27/1980'
print @BirthDate
print getdate()
SELECT 'DATEDIFF AGE = ', DATEDIFF(YEAR, @birthdate , GETDATE())
print 'TODAY IS THE TWENTY-SIXTH'
set @BirthDate = '08/26/1980'
print @BirthDate
print getdate()
SELECT 'DATEDIFF AGE = ', DATEDIFF(YEAR, @birthdate , GETDATE())

set @BirthDate = '08/25/1980'
print @BirthDate
print getdate()
SELECT 'DATEDIFF AGE = ', DATEDIFF(YEAR, @birthdate , GETDATE())

set @BirthDate = '08/24/1980'
print @BirthDate
print getdate()
SELECT 'DATEDIFF AGE = ', DATEDIFF(YEAR, @birthdate , GETDATE())

onecaring (10/12/2011)

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/*
Just use this function and get the exact age in "YYYMMDD" format (YearsMonthsDays)

average days in a year: 365.2425
average days ion a month: 30.436875

USAGE: SELECT dbo.udf_CalcAge('1960-01-01', '2011-10-12')
RESULT: "0510911" -- 51 YEARS, 9 MONTHS AND 11 DAYS

*/

CREATE FUNCTION [dbo].[udf_CalcAge] (@StartDate datetime = NULL, @EndDate datetime = NULL)

RETURNS varchar(7)

WITH EXECUTE AS CALLER

AS
BEGIN

RETURN (
RIGHT('000' + CAST(FLOOR(DATEDIFF(dd, @StartDate, @EndDate) / 365.2425) AS VARCHAR(3)), 3)+
RIGHT('00' + CAST(FLOOR((DATEDIFF(dd, @StartDate, @EndDate) / 365.2425) % 1 * 12) AS VARCHAR(2)), 2) +
RIGHT('00' + CAST(FLOOR(ROUND(((DATEDIFF(dd, @StartDate, @EndDate) / 365.2425) % 1 * 12) % 1 * 30.436875, 0)) AS VARCHAR(2)), 2)
)

END;

onecaring (10/13/2011)

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Interesting find. When does someone turn EXACTLY 1 year old? Or any full year old? Or when does 24 O'Clock happen? I guess it does happen but for such a nano second that it is almost impossible to get to that fraction. Or is it save to say never?

One is either one this side of the line or on the other side but never ON the line when it comes to such precision like exactly one year old or exactly 24 O'Clock time.

It is only my opinion... no one has to agree but positive criticism is most welcome