How can I Select date as MM/DD/YY format from the database

In the database there is one field name with datatype as datetime and the value is 2013-05-21 23:33:01 and i want to select date only from this field with user defined format as MM/DD/YY or DD-MM-YYYY...............
SELECT a.customer_name, b.customer_address, a.po_no, a.po_qty, cast(a.po_date As Date) as podate, cast(a.supply_date As Date) as sdate FROM device_order a INNER JOIN customer_details b ON a.customer_name = b.customer_name
In po_date and supply_date i want to fetch date as my format....
...