A GMT watch tells time in two different time zones, doing so with utmost simplicity. When a watch has a GMT function it means that the watch has a dial with 24-hour index and that the hand of the dial completes one full rotation in 24 hours. Implemented usually with a sub-dial, that can be set to a different time than the main dial, the watch can keep time in two time zones. There are also other implementations of the GMT function, e.g. 24 hour markings on the bezel, but the sub-dial version is the most common. First designed for PanAm pilots at the dawn of the Jet Age in the early 1950s, these distinct watches are a must for any traveller. These watches offer both fascinating history and the simplest way of keeping time wherever you might be in the world, whatever the time.