You're kidding, right?

Look at the to_date function ( http://technet.oracle.com/docs/produ...0datyp.htm#814 )

Look at the Date format models at ( http://technet.oracle.com/docs/produ...elem.htm#34926 )

Look at CREATE FUNCTION ( http://technet.oracle.com/docs/produ...pckgs.htm#4183 )