GMT watches explained

March 12, 2025

Closeup shot of the hands, numbers and hour marks of a black watch

In the world of watch complications, few are as practical and globally relevant as the GMT function. Born in the golden age of international air travel, GMT watches have evolved from specialized pilot’s tools to essential companions for global travelers, remote workers, and international businesses.

I remember my first experience with a GMT watch—tracking a conference call between colleagues in London, New York, and Singapore. That simple extra hand saved me from embarrassing time zone math errors and ignited my appreciation for this elegant complication. And I’m clearly not alone, as GMT watches remain among the most popular and sought-after timepieces in the watch market.

But what exactly is a GMT watch? How does it work? And which ones should you consider if you’re in the market? Let’s explore this fascinating horological innovation that helps us stay connected across time zones.

What Exactly Is a GMT Watch?

GMT stands for “Greenwich Mean Time,” the mean solar time at the Royal Observatory in Greenwich, London. While modern timekeeping now uses Coordinated Universal Time (UTC) as the primary time standard, the term GMT has stuck in the watch world.

A true GMT watch allows you to track at least two time zones simultaneously, typically through an additional hand that makes one complete rotation every 24 hours (compared to the standard hour hand’s two rotations per day).

The Origin Story: Pan Am and the Rolex GMT-Master

The GMT watch as we know it today was born from a specific need in the 1950s. As commercial aviation expanded to transcontinental flights, pilots and flight crews needed a reliable way to track both their departure time zone and Greenwich Mean Time (the aviation standard).

Pan American Airways approached Rolex with this challenge, leading to the creation of the now-iconic GMT-Master in 1954. The watch featured a 24-hour hand and a rotating bezel with a 24-hour scale, allowing pilots to track two time zones at once. The distinctive red and blue “Pepsi” bezel wasn’t just a design choice—it visually separated day (blue) from night (red) hours.

This innovative solution to a practical problem has since become one of the most enduring watch complications, prized by travelers and collectors alike.

How GMT Watches Work: The Mechanisms Explained

The Four Basic Types of GMT Watches

Not all GMT watches operate the same way. Understanding the different types helps you choose the one that best suits your needs:

1. True GMT (Flyer or Traveler GMT)

How it works: The local hour hand can be adjusted independently in one-hour jumps without stopping the watch, while the GMT hand stays fixed to your reference time (usually home time).

Advantages: Ideal for travelers who change time zones frequently, as you can quickly adjust the local time without affecting the accuracy of the watch or losing track of home time.

Examples: Rolex GMT-Master II, Grand Seiko SBGM221, Omega Seamaster Planet Ocean GMT

2. Caller GMT (Standard GMT)

How it works: The GMT hand can be adjusted independently, while the local hour hand remains fixed to the main time.

Advantages: More affordable to manufacture and still allows tracking of two time zones. Ideal for those who stay in one place but need to track a different time zone (like calling international colleagues).

Examples: Tudor Black Bay GMT, Seiko Presage Sharp Edged GMT, most affordable GMT watches

3. Fixed GMT

How it works: Both hour hands are linked and cannot be adjusted independently. The second time zone is set by rotating an external bezel.

Advantages: Mechanical simplicity and typically lower cost. Works well for tracking temporary time differences.

Examples: Timex Q GMT, many GMT quartz watches

4. Worldtimer

How it works: Strictly speaking, this is not a GMT but a more advanced complication. Worldtimers display multiple time zones simultaneously using a rotating city disc or bezel coordinated with a 24-hour ring.

Advantages: Allows tracking of all 24 major time zones at once. Ideal for global business or those who work with multiple international locations.

Examples: Patek Philippe World Time, Vacheron Constantin Overseas World Time, Frederique Constant Worldtimer

Key Components of a GMT Watch

Understanding the parts that make a GMT function work helps appreciate the ingenuity behind these timepieces:

24-Hour Hand

This additional hand makes one complete rotation every 24 hours, as opposed to the standard hour hand’s two rotations per day. It’s typically distinguished by a different color or arrow-shaped tip for easy identification.

Rotating Bezel or Fixed Scale

Most GMT watches feature either:

A rotating 24-hour bezel (allowing tracking of a third time zone)
A fixed 24-hour scale on the dial or chapter ring

Movement Modifications

The GMT function requires specific modifications to the base movement:

An additional gear train for the GMT hand
In true GMTs, a complex mechanism that allows independent adjustment of the local hour hand
In some higher-end models, specialized jumping hour mechanics for seamless time zone changes

How to Use a GMT Watch: Practical Applications

One of the most common questions about GMT watches is how to actually use them effectively. Here’s a straightforward approach:

Setting Up Your GMT Watch

For True GMTs (Traveler GMTs):

Set the GMT hand to your home time using the 24-hour scale
Set the local hour hand to your current location
When traveling, simply jump the hour hand forward or backward to match your new time zone
Your GMT hand continues to display home time

For Caller GMTs:

Set the main hands (hour, minute, second) to your local time
Set the GMT hand to the second time zone you want to track
When traveling, you’ll need to reset the entire watch to your new local time, then adjust the GMT hand again

Tracking a Third Time Zone

Many GMT watches with rotating bezels can track a third time zone:

Keep the main hour hand on local time
Keep the GMT hand on your home or reference time
Rotate the bezel to align with the third time zone
Read the third time zone by seeing where the GMT hand points on the bezel

Travel Scenarios and Examples

Business Travel Example:

You live in New York and travel to London for business
Before departure: Local hands show New York time, GMT hand shows Greenwich Mean Time
After arrival: Adjust local hour hand to London time (+5 hours), GMT hand still shows home time in New York

Remote Work Example:

You’re based in Los Angeles but work with a team in Tokyo
Local hands show Los Angeles time
GMT hand is set to Tokyo time (+16 hours)
Rotate the bezel to set a third time zone for your European clients

Popular GMT Watch Models Across Price Points

The GMT complication appears across the price spectrum, from affordable options to high-end luxury timepieces.

Entry-Level GMT Watches ($250-$1,000)

Seiko 5 Sports GMT SSK003/005

Price: ~$475
Features: Caller GMT function, rotating bezel, 100m water resistance
Movement: Seiko 4R34 automatic
Why it’s great: Incredible value proposition with a serious mechanical GMT movement in Seiko’s reliable and affordable 5 Sports line. Available in popular “Pepsi,” “Batman,” and black bezel variants.

Baltic Aquascaphe GMT

Price: ~$1,105
Features: Caller GMT, sapphire bezel, 100m water resistance
Movement: Swiss Soprod C125 automatic
Why it’s great: Vintage-inspired design with modern reliability and multi-colored sapphire bezel options. An affordable Swiss-powered GMT with exceptional build quality.

Lorier Hyperion GMT

Price: ~$599
Features: Caller GMT, bidirectional bezel, 100m water resistance
Movement: Miyota 9075 automatic
Why it’s great: Classic proportions (39mm) with vintage styling and a versatile design that works with both casual and formal attire.

Mid-Range GMT Watches ($1,000-$5,000)

Tudor Black Bay GMT

Price: ~$4,050
Features: Caller GMT function, aluminum bezel, 200m water resistance
Movement: Tudor MT5652 automatic with 70-hour power reserve
Why it’s great: Robust build quality, excellent movement, and the iconic “Pepsi” bezel at a more accessible price point than its Rolex cousin.

Monta Atlas

Price: ~$1,950
Features: True GMT function, fixed 24-hour scale, 150m water resistance
Movement: Modified Sellita SW330 automatic
Why it’s great: One of the most affordable True GMT watches with excellent finishing and a versatile 38.5mm case size.

Grand Seiko SBGN003

Price: ~$3,200
Features: True GMT function, fixed 24-hour scale, 100m water resistance
Movement: Grand Seiko 9F86 quartz with ±10 seconds per year accuracy
Why it’s great: Incredible accuracy, true GMT functionality, and Grand Seiko’s renowned finishing make this a perfect travel companion.

Luxury GMT Watches ($5,000+)

Rolex GMT-Master II

Price: ~$10,550+ (significant market premiums for most models)
Features: True GMT function, ceramic bezel, 100m water resistance
Movement: Rolex 3285 automatic with 70-hour power reserve
Why it’s great: The original GMT watch continues to set the standard with its robust construction, timeless design, and flawless functionality.

Omega Seamaster Planet Ocean 600M GMT

Price: ~$8,100
Features: True GMT function, ceramic bezel, 600m water resistance
Movement: Omega 8906 Co-Axial automatic with METAS certification
Why it’s great: Combines serious dive watch capabilities with a true GMT function and Omega’s impressive anti-magnetic technology.

Grand Seiko SBGE257 Spring Drive GMT

Price: ~$6,200
Features: True GMT function, ceramic bezel, 200m water resistance
Movement: Grand Seiko 9R66 Spring Drive with ±1 second per day accuracy
Why it’s great: Spring Drive’s unparalleled smoothness and accuracy combined with true GMT functionality and Grand Seiko’s exceptional finishing.

GMT vs. World Time vs. Dual Time: Understanding the Differences

These terms are often used interchangeably, but they refer to different complications:

GMT

Displays two time zones using a 24-hour hand
Typically features a rotating bezel that can track a third time zone
Designed primarily for tracking specific reference time zones

World Time

Displays all 24 major time zones simultaneously
Features a rotating city disc or bezel representing major cities in each time zone
Allows for quick reference to any global time zone without adjustment

Dual Time

Displays two complete time displays, often with separate dials
Both displays typically use a 12-hour format
May have separate movements or a single movement with dual displays

The key distinction is that GMT watches are purpose-built for tracking specific time zones (typically your home and current location), while world timers provide a global overview and dual time watches offer two complete time displays.

Tips for Buying Your First GMT Watch

If you’re considering adding a GMT watch to your collection, here are some factors to consider:

True GMT vs. Caller GMT

Choose a True GMT if:

You travel frequently across time zones
You value convenience when changing time zones
You prefer keeping your home time as the reference

Choose a Caller GMT if:

You primarily stay in one place but need to track another time zone
You’re on a tighter budget (true GMTs typically cost more)
You don’t mind resetting the watch when you do travel

Size and Wearability

GMT watches often run slightly larger due to the additional mechanics, but modern options exist in various sizes:

38-39mm: Ideal for smaller wrists or those preferring vintage proportions
40-42mm: The most versatile size range, suitable for most wrists
43mm+: Better suited for larger wrists or those who prefer a bold presence

Bezel Type Considerations

Ceramic bezels offer scratch resistance and long-term color stability, but can be costly to replace if damaged.

Aluminum bezels are more traditional, develop character with age, and are typically less expensive to replace.

Sapphire bezels offer unique aesthetics with light play and excellent durability.

Bracelet vs. Strap

Most GMT watches come on bracelets, which is ideal for travel due to:

Durability during frequent wear
Ability to handle different climates and conditions
Easy adjustability for comfort in changing temperatures

However, many enthusiasts enjoy changing to leather or NATO straps to customize the look.

How to Care for Your GMT Watch While Traveling

GMT watches are built for travel, but they still benefit from proper care:

Time Zone Adjustment Best Practices

For mechanical GMTs, avoid changing the date or time when the watch is between 9 PM and 3 AM to protect the date mechanism
For true GMTs, use the jumping hour hand feature rather than the main crown time setting
Set your watch to the new time zone before landing when possible to minimize the rush upon arrival

Travel Storage and Protection

Use a travel watch case with sufficient padding
Remove your watch during security screening to avoid potential magnetization
Consider the local environment (humidity, temperature) in your destination and adjust storage accordingly

Water Resistance Considerations

Check crown and pushers are fully secured before exposure to water
Remember that temperature changes (like going from air-conditioned room to hot poolside) can affect water resistance
Have gaskets checked before extended travel, especially to humid or aquatic destinations

The Future of GMT Watches

As travel patterns and global connectivity evolve, so do GMT watches:

Emerging Trends

Hybrid functionality: GMT complications combined with other useful features like annual calendars
Size reduction: More compact GMTs becoming available for smaller wrists or vintage preferences
Material innovation: New case materials offering improved durability for frequent travelers
Enhanced accuracy: High-frequency movements and advanced regulation providing better timekeeping across time zones

Smart Integration

Some modern mechanical GMTs now incorporate limited smart features:

Bluetooth time zone synchronization
App-controlled time zone updates
Environmental adaptations for temperature and position

Sustainability Focus

The watch industry’s shift toward sustainability is affecting GMT watches through:

Recycled case materials
Ethically sourced components
Carbon-neutral manufacturing processes
More durable designs intended for multi-generational use

Conclusion: Why GMT Watches Endure

In an age when our phones automatically update to local time, why do GMT watches remain so popular? The answer lies in their elegant solution to a universal challenge—navigating our global world while staying connected to home.

Unlike digital alternatives, a mechanical GMT watch:

Works without batteries or charging
Provides an instant visual reference without waking a screen
Offers a tangible connection to the golden age of travel
Serves as both a useful tool and an expression of personal style

Whether you’re a frequent international traveler, working with global teams, or simply appreciating horological innovation, a GMT watch represents one of the most practical and enduring complications in watchmaking—a mechanical solution to our increasingly connected world.

Do you use a GMT watch? What’s your favorite model, and how do you use it in your daily life? Share your experiences in the comments below!