What Is a GMT Watch? Learn How It Works and How to Use It – A Complete Guide from King ReplicaChức Năng GMT

Are you puzzled by the term “what is a GMT watch” when reading the specifications of a luxury timepiece? Don’t worry—this article from King Replica explains everything you need to know, from history and mechanics to how to use the GMT function in daily life.

1. What Is a GMT Watch?

A GMT watch is a wristwatch capable of displaying two different time zones simultaneously. It usually features an additional GMT hand that rotates on a 24-hour scale, pointing to a second time zone on either a 24-hour dial or a rotating bezel. This smart configuration allows wearers to track local time and international time without adjusting the main hour hand.

GMT stands for Greenwich Mean Time—the time at the Prime Meridian (Longitude 0°), which serves as the global time reference point. Other time zones are defined by adding or subtracting hours from GMT (e.g., GMT+7 for Vietnam, GMT-5 for New York). Before UTC was adopted, GMT was the official international time standard.

2. History of the GMT Watch

So where did the idea for GMT watches originate? The design was born out of real-world needs in aviation and maritime industries, where monitoring multiple time zones was essential. In the early 1950s, as international travel surged, watchmakers began developing this feature for pilots and globetrotters.

In 1953, Glycine released the Airman—the first watch to show a second time zone using a 24-hour format. Just two years later, Rolex introduced the GMT-Master Ref. 6542, featuring a separate GMT hand and rotating 24-hour bezel. This model quickly became the go-to choice for Pan Am Airlines pilots, allowing them to track two or even three time zones using the rotating bezel.

Although GMT was replaced by UTC in 1972, most watch brands still use the “GMT” label to denote multi-time-zone capability. In 1983, Rolex launched the GMT-Master II, featuring an independently adjustable GMT hand—now the modern standard for high-end GMT watches.

3. Key Features of a GMT Watch

GMT watches offer unique features that allow users to track multiple time zones. So what exactly are these features?

• Independent GMT hand: This hand moves on a 24-hour cycle and is separate from the main hour hand. It displays a second time zone, useful for travelers or international business.
• Rotating 24-hour bezel: Enables tracking of a third time zone. The bezel often has clearly marked divisions to make reading easier.
• Dual scale layout: A 24-hour scale on the dial or bezel complements the traditional 12-hour scale, helping distinguish between AM and PM.
• Optional sub-dials: Some high-end models include sub-dials for additional time zones—ideal for frequent international travelers.

4. How Does a GMT Watch Work?

GMT watches add a fourth hand—rotating once every 24 hours—to the standard three-hand configuration. While the hour hand completes a full cycle every 12 hours, the GMT hand takes a full 24 hours, making it easy to differentiate between day and night.

The GMT hand points to a 24-hour scale located either on the bezel or the dial’s perimeter. Paired with a rotating bezel, this setup allows the wearer to track a second—and sometimes third—time zone by simply rotating the bezel.

Though simple in principle, this design is incredibly effective for people who work internationally or travel frequently. Some models even use a two-tone bezel (like Rolex’s blue-red “Pepsi” bezel) to distinguish day from night.

5. How to Use the GMT Function

Here’s a detailed guide to using the GMT function on your watch:

5.1 Understanding the Crown Positions

Most GMT watches have three crown positions. What does each crown position do on a GMT watch?

• Position 0 (locked): Keeps the case sealed against water and dust. Always return the crown to this position after setting.
• Position 1: Used for manual winding to power the movement. Does not adjust time or date.
• Position 2: Adjusts the main hour hand and date. The minute and GMT hands stay fixed.
• Position 3: Adjusts both the minute and GMT hands. The seconds hand usually stops, allowing for precise time-setting.

Note: Functions may vary slightly between models, so consult the manual or a technician to avoid damaging the movement.

5.2 Tracking Two Time Zones

To track two time zones simultaneously, use the GMT hand along with the 24-hour bezel:

• Step 1: Pull the crown to position 3 and set the GMT hand to your home time using the 24-hour scale. For example, if it’s 17:00 in Vietnam, position the GMT hand to 17.
• Step 2: Push the crown to position 2 and set the main hour hand to 5 o’clock on the 12-hour dial.
• Step 3: Rotate the bezel to set the second time zone. If Tokyo is at 19:00 (2 hours ahead), rotate the bezel two clicks clockwise until the GMT hand points to 19.
• Step 4: Return the crown to position 0.

Now, read your local time from the main hour hand (12-hour scale) and the second time zone from the GMT hand (24-hour scale on the bezel).

5.3 Tracking Three Time Zones

Some GMT models let you track a third time zone using the GMT hand and bezel combination:

• Step 1: Pull the crown to position 3 and set the GMT hand to GMT time (e.g., 10:00).
• Step 2: Push the crown to position 2 and set the main hour hand to local time.
• Step 3: Rotate the bezel based on the third time zone offset. For example, if the third time zone is GMT+6, rotate the bezel 6 clicks clockwise.
• Step 4: Push the crown back to position 0.

Now you can read local time, GMT time, and a third time zone all at once.

So now you know the answer to “what is a GMT watch?” If you’re drawn to iconic GMT models like the Rolex GMT-Master II but aren’t ready to invest in an original, our collection of luxury replica watches offers high-precision alternatives. Designed to closely mirror the original in aesthetics, movement, and GMT functionality, these watches deliver exceptional value at a more accessible price point.