Depending on your regional settings, the parameter you are passing in for @TimeItemAdded might not be recognized.

You should pass the date in as:

20120720

Well, when passing the parameter values to the dataset, first you need to convert your input parameter values to the list of CSV values.

For example, if your parameter is like:

With properties such as:

You should consume that in your dataset using JOIN function.

e.g.:

=JOIN(Parameters!input.Value,",")

It should look like:

Now, your dataset will view/receive @input as '123,456,789'

And, now you can use any split function to split the values and can use them in your SQL.

In case if there is no split function available, you can use any custom SQL (an example given below) to change the multiple values to a single-valued table:

e.g.:

DECLARE @input VARCHAR(MAX) = '123,456,789'
IF OBJECT_ID('TEMPDB..#Multi') IS NOT NULL DROP TABLE #Multi;
CREATE TABLE #Multi (value  INT);
DECLARE @Insert VARCHAR(MAX) = 'INSERT INTO #Multi VALUES ('''+REPLACE(@input,',','''),(''')+''');';
EXEC (@Insert);
SELECT value FROM #Multi

Will return following output:

And you final SQL should be SQL chunk given above and:

SELECT * FROM A
WHERE Id IN (SELECT value FROM #Multi)

OR

SELECT * FROM A
JOIN #Multi M ON A.Id=M.value

Hope this help.

Bad news: social security number isn't in the format of DDMMYYXXXX. (My own SSN starts with a number above 3, for example.)

Take out the DATEDIFF and CONVERT functions, and just look at the source data. You'll likely see the offending rows just by eyeballing it:

SELECT Users.Id, Users.FirstName + ' ' + Users.LastName AS Medarbajder, Users.SSN AS CPRNR, SupposedlyDate AS STUFF(STUFF(LEFT(Users.SSN, 6), 3, 0, '.'), 6, 0, '.'), FROM dbo.Paychecks, dbo.Users WHERE Users.CustomerId=214 AND Users.Id=Paychecks.UserId order by 4;

I don't know where you got that formula from, but it doesn't work. (It certainly doesn't produce a valid date for my own SSN.) There are ways to guess approximate dates from social security numbers, but not produce valid birth dates.