No, the problem is that you think it does, and it does not. SQL SERVER 2005 stores dates as datetime. Even your own DOB column which you defined in your first post:

Table -> Person

Field -> DOB

type -> datetime

Computed-> no

Nullable-> yes

There's no need to convert it to a string or anything else, just use the built-in DATETIME functions:

-- make up some sample DOB data

DECLARE @person TABLE (id INT, name VARCHAR(100), dob DATETIME)

INSERT INTO @person

SELECT 1, 'p1', '1948-12-30 00:00:00.000'

UNION SELECT 2, 'p2', '1958-12-31 00:00:00.000'

UNION SELECT 3, 'p3', '1968-01-01 00:00:00.000'

UNION SELECT 4, 'p4', '1982-01-02 00:00:00.000'

UNION SELECT 5, 'p5', '2004-04-04 00:00:00.000' -- Happy Birthday to me!

UNION SELECT 6, 'p6', '2005-04-16 00:00:00.000' -- 12 days away

UNION SELECT 7, 'p7', '2006-04-25 00:00:00.000' -- 21 days away

UNION SELECT 8, 'p8', '2007-05-05 00:00:00.000'

UNION SELECT 9, 'p9', '2008-05-20 00:00:00.000'

UNION SELECT 10, 'p10', '2009-05-25 00:00:00.000'

-- show how the algorith works

DECLARE @Today DATETIME, -- allows you to change the "current date" for testing

@WarningDays INT

SET @Today = DATEDIFF(DAY, 0, GETDATE()) -- set the time-stripped "current date"

SET @WarningDays = 15

SELECT *,

DATEDIFF(YEAR, dob, @Today), -- number of year boundaries crossed since DOB

DATEADD(yy, DATEDIFF(YEAR, dob, @Today), dob), -- add to DOB to give birthday this year

DATEDIFF(dd, @Today, DATEADD(yy, DATEDIFF(YEAR, dob, @Today), dob)) -- compare with current date to yield number of days until birthday

FROM @person

id name dob YearBounds Birthday DaysToBD

----------- ---- ----------------------- ----------- ----------------------- -----------

1 p1 1948-12-30 00:00:00.000 61 2009-12-30 00:00:00.000 270

2 p2 1958-12-31 00:00:00.000 51 2009-12-31 00:00:00.000 271

3 p3 1968-01-01 00:00:00.000 41 2009-01-01 00:00:00.000 -93

4 p4 1982-01-02 00:00:00.000 27 2009-01-02 00:00:00.000 -92

5 p5 2004-04-04 00:00:00.000 5 2009-04-04 00:00:00.000 0

6 p6 2005-04-16 00:00:00.000 4 2009-04-16 00:00:00.000 12

7 p7 2006-04-25 00:00:00.000 3 2009-04-25 00:00:00.000 21

8 p8 2007-05-05 00:00:00.000 2 2009-05-05 00:00:00.000 31

9 p9 2008-05-20 00:00:00.000 1 2009-05-20 00:00:00.000 46

10 p10 2009-05-25 00:00:00.000 0 2009-05-25 00:00:00.000 51

-- use the algorithm

DECLARE @Today DATETIME, -- allows you to change the "current date" for testing

@WarningDays INT

SET @Today = DATEDIFF(DAY, 0, GETDATE()) -- set the time-stripped "current date"

SET @WarningDays = 15

SELECT *,

DATEDIFF(dd, @Today, DATEADD(yy, DATEDIFF(YEAR, dob, @Today), dob)) AS DaysToBD

FROM @person

WHERE DATEDIFF(dd, @Today, DATEADD(yy, DATEDIFF(YEAR, dob, @Today), dob)) BETWEEN 0 AND @WarningDays

id name dob DaysToBD

----------- ---- ----------------------- -----------

5 p5 2004-04-04 00:00:00.000 0

6 p6 2005-04-16 00:00:00.000 12