GMT and Dual-Time Complications
The GMT complication takes its name from Greenwich Mean Time, the reference standard for civil aviation until its formal replacement by Coordinated Universal Time (UTC) in 1972. The first wristwatch GMT specifically designed for pilots was Rolex's reference 6542, introduced in 1955 in collaboration with Pan American World Airways for its transcontinental flight crews.
True GMT vs office GMT
A 'true' or 'flyer' GMT lets the local hour hand jump in one-hour increments without stopping the seconds, leaving the 24-hour hand on home time - the configuration crews actually need when crossing time zones. An 'office' or 'caller' GMT instead moves the 24-hour hand independently, which suits travellers who keep their watch on home time and reference a second zone for calls.
Notable references
Rolex GMT-Master (1955) and the modern GMT-Master II (1983, true-GMT); Glycine Airman (1953, 24-hour rotating bezel); Omega Seamaster Aqua Terra GMT; Grand Seiko's Spring Drive GMT calibre 9R66; Tudor Black Bay GMT (2018), one of the most accessible true-GMT options on the market.
Reading a 24-hour bezel
Two-tone bezels - the original 'Pepsi' red/blue or the later 'Coke' red/black - divide the bezel between daylight and night-time hours, making the second zone readable at a glance.
Key facts
- ▸First pilot-grade GMT wristwatch: Rolex 6542 (1955).
- ▸True GMT = independent local hour hand; office GMT = independent 24-hour hand.
- ▸GMT formally superseded by UTC for civil aviation in 1972.