watchionary

A GMT watch is a timepiece that shows both the 24-hour and 12-hour time scales. In other words, instead of twice a day, the 24-hour hand circles the dial once a day, its tip pointing to the corresponding hour, removing any doubt about whether it's a.m. or p.m. The 24-hour clock hands are usually of a different colour and rotate half as fast as the 12-hour hands.