TonyD -- "I was wondering can we use all of our sick leave before retirement? For example if I have one year worth of SL, can I take it all at once before my retire date? "
-- Willing to risk not being really sick or getting injured before retirement?
-- To be clear: Are you talking about 13 days of sick leave or you have 365 days of sick leave, as both represent one year worth of SL.
-- Depending on office manning, manglement MAY allow you to take 13 days off leading up to retirement.
-- In the other case, very doubtful you could get a year off using accumulated sick leave -- unless you go over to the "dark side" and become a member of manglement.