date format problem

hi all,

suggest me some function module for date format( from dd.mm.yyyy to yyyymmdd).

when i am passing sy-datum through bdctable to f-53 transaction code screen.

in sy-datum i have <b>dd.mm.yyyy</b>. and when it goes to on screen (in document date,and in posting date field) it change into to <b>yyyymmdd</b>.

In the table(bkpf) that fields stored as yyyymmdd only. i think due to this ,its happen.

how do i sove that problem.

thank you.