n the 1950s the growing number of aeroplanes crossing time zones in all directions made the adoption of a single reference time – valid for every aircraft, in all locations, whatever the local time – a necessity. By adopting Greenwich Mean Time (GMT) as the time of reference for all aeroplanes, air traffic controllers and flight plans, it was finally possible to prevent the sort of confusion that could have dire consequences. It was the birth of the famous ‘Zulu time’.

One brand instantly understood the full potential of this decision: Rolex. In collaboration with the famous Pan Am company, in 1954 Rolex launched the GMT Master, reference 6524, which has become the ‘mother’ of all GMT watches.

The principle was simple, the design ergonomic, the function highly practical, and time setting was child’s play. And it was a runaway success.

A fourth luminescent hand, instantly recognisable with its arrow shape, travels around the dial in 24 hours, pointing to a rotating bezel with 24 graduations. It is independently adjusted by the crown in position 2. The arrow is set to indicate the time of departure – Zulu time for aviators, home time for their passengers – then, without interfering with the minutes and seconds, the 12-hour current time hand is set to the time zone you are currently crossing or that of your destination. Nearly every brand quickly followed suit. Breitling, which with its Breitling Navitimer had already collaborated actively with the world of aviation and was the official timekeeper for the Aircraft Owners and Pilots Association (AOPA), began releasing GMT models in the early 1960s. It introduced the Chrono-Matic, combining a dual time zone with GMT hand and a manually-wound chronograph.

Rolex GMT

The Rolex GMT-Master II needs no introduction. Pictured here in its most recent version, it features a Cerachrom rotating bezel, Parachrom balance spring, Oyster bracelet, Triplock winding crown and self-winding 3186 movement.

In 1969 it was Omega’s turn to launch its Flightmaster series, ‘for intercontinental travellers’. Using seven brightly-coloured contrasting hands, three crowns and two push-pieces, the wearer can activate a chronograph with interior rotating bezel and move a bright blue GMT hand in the shape of an aeroplane.

All this is housed in a large, oblong-shaped case. Production continued until the mid-’70s. Practically every watch brand released something similar and there are countless GMT watches, as well as those opting for a different configuration but with the same functions – known as ‘dual time zone’ watches. More ‘civilian’ and less ‘professional’, dual time zone watches allowed for all display types, therefore departing from the sporty aesthetic of the GMT. They were, in their way, the dressier version of the traveller’s watch – also ideal for non-travellers.