One of two different clocks is installed on the right side of the center instrument panel. The clock provides the time and date to all aircraft systems that require time, including the FMGCs and ACARS. (ACARS receives time from the clock; there is no provision to update the clock from ACARS.)
One clock is fully self-contained. It has an analog chronometer needle that sweeps around the clock face. The time and date must be manually set if the clock is not correct.
The other clock is fully digital. It normally synchronizes to and displays GPS time, but can be set to disregard the GPS and display its own internal time and date, which can be manually set.