Getting the Date Difference in Years, Months and Days

CREATE PROCEDURE dbo.CalculateAge
@dayOfBirth datetime
AS

DECLARE @today datetime, @thisYearBirthDay datetime
DECLARE @years int, @months int, @days int

SELECT @today = GETDATE()

SELECT @thisYearBirthDay = DATEADD(year, DATEDIFF(year, @dayOfBirth, @today), @dayOfBirth)

SELECT @years = DATEDIFF(year, @dayOfBirth, @today) - (CASE WHEN @thisYearBirthDay > @today THEN 1 ELSE 0 END)

SELECT @months = MONTH(@today - @thisYearBirthDay) - 1

SELECT @days = DAY(@today - @thisYearBirthDay) - 1

select @thisYearBirthDay
SELECT @years [Years], @months [Months], @days [Days]