GMT / Dual Time

Why it matters

GMT and dual time both describe a watch that displays a second time zone alongside the local one. The term GMT comes from Greenwich Mean Time, the global reference standard before UTC replaced it. The mechanism is straightforward: an extra hour hand reads against a 24-hour scale, often on the bezel, so the wearer can read a second zone at a glance.

In watch listings, GMT functionality affects price meaningfully. A Rolex GMT-Master II commands a premium over a same-era Submariner partly because of the complication. When evaluating a GMT listing, two technical questions matter: whether the local hour hand is independently adjustable (a true caller GMT vs a flyer GMT), and whether the 24-hour bezel is bidirectional. Caller GMTs let you change the home zone without stopping the watch; flyer GMTs let you jump the local hour hand in one-hour increments without disturbing the minute hand. Both are useful; flyer is more travel-friendly.

Common questions

What is a GMT watch?

A GMT watch displays a second time zone alongside the local one, using an extra hour hand that reads against a 24-hour scale. The name comes from Greenwich Mean Time, the global reference standard. Modern GMT watches are popular with travelers and people coordinating across time zones.

What's the difference between a caller GMT and a flyer GMT?

A caller GMT lets you adjust the GMT (second time zone) hand independently while keeping the local time running. A flyer GMT lets you jump the local hour hand forward or backward in one-hour increments without stopping the watch. Flyer is more useful for travelers; caller is better for staying connected to a home zone.

Related terms

• Complication

  Any function beyond basic timekeeping: chronograph, moon phase, perpetual calendar, tourbillon, GMT, etc.

• Pepsi(Pepsi Rolex, Pepsi GMT)

  Rolex GMT-Master / GMT-Master II with a red and blue bezel. The most iconic Rolex nickname, inspired by the Pepsi logo color scheme.

• Batman(Batman Rolex, Batman GMT)

  Rolex GMT-Master II with a blue and black ceramic bezel on an Oyster bracelet.

• Root Beer

  Rolex GMT-Master with a brown and black (or brown and gold) bezel, reminiscent of root beer coloring.