A hand, usually on a sub-dial, which completes a rotation in 24 hours and enables the wearer to read the 24-hour time, e.g. 16:00 instead of 4 p.m.

A GMT function means that the watch has a second hour hand which completes one full rotation in 24 hours and a 24-hour index on the dial. Particularly useful for wearers who wish to track two time zones.