For DCS, iDCS and OS7XXX series Samsung telephone systems.
Without lifting the handset, hit the transfer button and then dial 200. When asked for the passcode enter 1234. The display will show disabled, enter 1 to change it to enabled and hit the transfer button again.
Now hit the transfer button and dial 505. The display will show the current date and time in the top row and WMMDDYY:HHMM Enter the new information as follows