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.
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- GMT — Greenwich Mean Time, the historical reference for the second time zone display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.
Related photographs
.jpg)
No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- General horological literature on the development of pilot GMT watches.
Where sources disagree, the disagreement is stated rather than resolved silently.