What Is a GMT Watch? Meaning, Function, and How It Works

A GMT watch is one of the most useful timekeeping complications for frequent travelers, pilots, international professionals, and anyone who communicates across time zones. Though often confused with dual time zone watches, the GMT watch features a 24-hour hand that allows wearers to easily track an additional time zone—or even a third.

In this article, we’ll break down what “GMT” means, how a GMT watch works, and why it remains one of the most iconic and practical complications in horology.

What Does GMT Mean on a Watch?

GMT stands for Greenwich Mean Time, which was established as the standard time at the Prime Meridian (zero degrees longitude) in Greenwich, London. Prior to global time standardization, local solar time was used—leading to inconsistencies, especially in railway and maritime schedules.

In 1884, GMT was officially adopted as the world’s timekeeping standard. Although Coordinated Universal Time (UTC) replaced GMT in 1972 for scientific purposes, GMT remains a common term in the watch world.

Example time zones:

• Hong Kong: GMT +8
• Dubai: GMT +4
• Philadelphia: GMT -5

How Does a GMT Watch Work?

The GMT function was popularized in the 1950s when Pan Am asked Rolex to create a timepiece for pilots flying across multiple time zones. The result was the Rolex GMT-Master “Pepsi”, featuring an extra hand on the dial and a 24-hour bezel.

A standard GMT watch includes:

• A fourth hand (usually arrow-shaped and in a distinct color)
• A 24-hour scale, either printed on the dial or on a rotating bezel

This 24-hour GMT hand rotates once per day and is used to track a second time zone. Some modern GMT watches feature independent GMT hands, which allow for even greater functionality, including tracking a third time zone.

What Is the Difference Between a GMT Watch and a Dual Time Watch?

A GMT watch uses a 24-hour scale to indicate day/night and track time in two or more zones. A dual time zone watch usually has a second 12-hour dial or sub-dial without a 24-hour reference. If it doesn’t include an AM/PM indicator, it can be harder to know if it’s day or night in the second time zone.

Using the Bezel

Depending on your watch, the GMT hand may be anchored to the hour hand. As you adjust the local time, the GMT hand will move with it. For the second timezone, you would simply turn the bezel to align with the proper hour. There have been advancements in the movements and many brand’s product models with independent GMT hands. The bezel still rotates bi-directionally for easy setting of the time.

Not all GMT watches feature an hour-scale bezel. The Seamaster Aqua Terra GMT, for example, features the 24-hour scale printed between the indices on the dial.

How to Read and Set a GMT Watch

Static GMT Hand

1. Align the bezel with the 12 o’clock marker.
2. Set the GMT hand to GMT or your second time zone.
3. Rotate the bezel to reflect a third time zone, if needed.

Independent GMT Hand (e.g., Rolex GMT-Master II)

1. Set the GMT hand to your home time (24-hour scale).
2. Set the local hour hand to your current location.
3. Rotate the bezel to track a third time zone, using GMT as your anchor.

Note: Watches like the Omega Seamaster Aqua Terra GMT have a fixed 24-hour scale on the dial rather than a rotating bezel.

Using a GMT To Track A Third Timezone

Because many modern GMT functions feature an independent GMT hand, it is possible to track a third timezone by using the GMT hand and 24-hour bezel. To accomplish a third timezone, you will set the GMT hand to current GMT time, and the hour hand set to local time. The bezel can then be rotated to set a third timezone, using GMT as the reference for how many hours to add or subtract, rotate either clockwise or counterclockwise depending on location. The bezel would then align with the third timezone and GMT hand, your local time would be read by the hour hand. It is important to note that the second timezone would need to have the bezel rotated back for reading the time.

Can You Use a GMT Watch as a Compass?

Yes. In the Northern Hemisphere, point the GMT hand at the sun:

• The 12 o’clock marker on the bezel will then point north.

In the Southern Hemisphere, the reverse applies:

• Point the GMT hand at the sun, and the 12 o’clock marker points south.

Who Uses a GMT Watch?

GMT watches are ideal for:

• Pilots
• Frequent travelers
• Military personnel
• Business professionals with global clients
• Collectors and enthusiasts

It’s also a practical choice for those with family abroad or anyone managing international schedules.

Popular GMT Models

Because of its popularity, the GMT function is found throughout a number of brands and models. Some of the most popular GMT watches include:

• Rolex GMT-Master II
• Tudor Black Bay GMT
• Omega Seamster Aqua Terra GMT
• Rolex Sky-Dweller
• Grand Seiko Heritage Spring Drive GMT
• Breitling Chronomat
• Oris Aquis

Final Thoughts: Why Choose a GMT Watch?

Beyond its heritage and technical innovation, a GMT watch combines style, precision, and utility. Whether you’re navigating different time zones, managing a global team, or simply fascinated by horology, a GMT watch offers a tangible connection to the world.

Not all dual time watches are true GMTs. If a watch lacks a 24-hour hand or AM/PM indicator, it functions differently.

Discover the latest GMT watches at The 1916 Company or shop the entire collection of authorized new watches,  pre-owned luxury watches, or Rolex Certified Pre-owned watches to find your perfect timepiece.