The present invention concerns the field of watches and time pieces. There is disclosed a mechanism for a watch (10) configured so that heartbeats act as the trigger that initiates updating of a second unit display. There is also described a mechanism for a watch adapted so that a heartbeat acts as a trigger to increment the time display (21). Furthermore there is disclosed a watch which is associated with a heartbeat sensor (30), the watch being adapted to periodically update a time display in response to heartbeats detected by the sensor, whereby the time display is updated every time a heartbeat is sensed.