FYI - I asked because IME there is a good chance you may want to get records based on the date value in the future. Having it this way makes your table and the data in it less powerful SQL wise...
I am not aware of any way to append leading zero's to date type values directly. I guess if I had to do it (after strongly suggesting this data type should be changed - all your SQL inserts and updates already have "' & & "' around them. Anyhow enough of that... I would build a function which:
> breaks the date apart (maybe into three variables D, M Y)
> check then len of the D and M
> if len < 1 then append a leading 0
> build string back together
That would be one way to skin your cat
Wind is your friend