This allows the programmer to set the internal clock on the unit. Since there is no battery backup on board, once power is removed from the unit, the internal clock resets to "00/00 00:00:00". This command may never have to be used, due to the following: On the first incoming call with Caller ID and a good checksum, the internal time clock will be set to the time sent in the Caller ID signal. On every call thereafter, the internal clock is reset to the Caller ID time. The format for time entry using the "Z" command is mm (month), dd (day), hh (hour), and mm (minute)

Since the time sent on a Caller ID signal does not include seconds, the internal time clock may differ from by as much as 59 seconds from the last call.