Watch family · Complication
Dual Time / GMT Watches
VerifiedWatches displaying two time zones at once, typically via an additional 24-hour hand and rotating or fixed bezel, developed initially for airline navigators and pilots.
How the mechanism works
The mechanism behind these watches — how it is built, how it developed and its variants — is explained on the Dual time / GMT page and the related pages below. This page covers what is particular to the watches themselves: identification, terminology and collecting.
Movement & mechanism
- An additional hand geared to complete one revolution every 24 hours (rather than 12), pointing to a 24-hour scale usually on a rotating bezel
- Independently adjustable hour hand in many modern designs, allowing local time to be changed without disturbing the GMT hand or minutes
- Simpler designs use a fixed 24-hour hand read only against a static bezel scale
Identification
- A fourth hand, usually arrow-tipped, distinguishable from the hour/minute/seconds hands
- A rotating or fixed bezel marked 0–24
Terminology
- GMT — Greenwich Mean Time, the historical reference for the second time zone display
- True GMT / caller GMT — modern terms distinguishing independently adjustable local-hour designs from simpler fixed-GMT-hand designs
Known variations
- Fixed-bezel GMT
- Rotating-bezel GMT
- Independent (true GMT) hour-hand design
Pocket-watch ancestry
Dual-time indications have limited pocket-watch precedent; this is substantially a wristwatch-era complication responding to the specific needs of mid-twentieth-century commercial aviation.
Collecting notes
A major modern tool-watch category, closely associated with the history of commercial and military aviation timekeeping.
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- General horological literature on the development of pilot GMT watches.
Where sources disagree, the disagreement is stated rather than resolved silently.