Question concerning Oracle 8i and Format Mask command

I have a question concerning Oracle 8i and Format Mask command.

Here is the record in question:

SELECT s_first, s_last
FROM student
WHERE s_class = 'FR'
OR s_dob < TO_DATE('01-JAN-1981', 'DD-MM-YYYY');

Why is it necessary for the 'DD-MM-YYYY' after the date? When I origionally inserted the values into the table, I already entered the date in the format '01-JAN-1981', 'DD-MM-YYYY. I tried writing the query without the DD-MM-YYYY, and it returned the same results.

Thanks
John Received on Wed May 22 2002 - 19:57:50 CDT