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Long the preserve of a very specific audience, the GMT complication has been having quite a moment lately. Adding just a single hand to our timepieces, it proves that in watchmaking, the smallest detail can make all the difference - and sometimes even simplify daily life for a whole range of people, particularly high-flying professionals.
The bottom line: this is anything but a gimmick - and here's exactly why.
Contrary to what some might think, GMT isn't just a watch complication. Behind those three letters is actually the term "Greenwich Mean Time" - a global reference system that divides the planet into different time zones. That's precisely why it's not the same time in New York and Paris.
If you've read our guide to the history of watchmaking, you already know that "GMT" is a system established to simplify exchanges between different regions of the world by setting a universal time standard. Before that, time could vary not only from one country to another, but from one city to the next - even within small territories. Clocks like those found in railway stations, for instance, were set according to their location and the position of the sun. Looking back, it's all pretty remarkable, isn't it?
It was at the International Meridian Conference in Washington, in 1884, that common rules were established, simplifying the organization of time zones on a global scale. For nearly a century, GMT remained the standard, still based on the position of the sun as its foundation.
Members of the International Meridian Conference, Washington, 1884 (Source: Wikipedia)
It wasn't until 1972 that a transition toward UTC - "Coordinated Universal Time" - began. This system, based on atomic clocks, delivers unmatched precision. It's worth noting that UTC doesn't correspond exactly to a time zone system, but rather to a reference time scale that makes it possible to know the exact time anywhere in the world.
World time zone map GMT & UTC (Source: Wikimedia)
So there you have it - a quick overview of what GMT actually is! But let's get back to what really matters in this guide: the GMT complication as found on certain watches.
While this function is most commonly referred to as "GMT," some watch manufacturers - such as Sinn, MAT, Rado, Formex, and IWC - prefer the term "UTC" for their models. This choice is likely rooted in the historical context we've just discussed. Either way, just keep in mind that "GMT watch" and "UTC watch" refer to exactly the same thing.
So what does this complication actually do? The GMT function displays two time zones simultaneously on a single watch. It's especially useful for frequent international travelers - globe-trotters, flight crews, airline pilots. Anyone with family or contacts in other countries will also find it genuinely convenient.
The GMT Complication: A Traveler's Best Friend
On a GMT watch, the primary time zone is displayed just like on a standard watch - on a 12-hour scale - using an hour hand, a minute hand, and a seconds hand. The second time zone is shown by a dedicated hand called the "GMT hand," which completes one full rotation of the dial every 24 hours. To read this hand, you refer to the scale most commonly found (though not always) on what is called a "GMT bezel."
GMT Bezel and Hand
But - we'll leave it at that for now. If you want to dive deeper into how the GMT complication works, just keep reading.
The GMT complication is deeply rooted in the history of aviation. The very first wristwatch equipped with this function has an origin that is as technical as it is romantic - designed to meet the specific needs of pilots. The idea came from Samuel W. Glur, a sales representative at Glycine who traveled frequently.
Portrait of Samuel W. Glur (Source: glycinetennial)
During his travels, he took the time to ask pilots what they considered the ideal pilot's watch. The answers were unanimous: they wanted a water-resistant timepiece capable of displaying a second time zone.
The message didn't fall on deaf ears. Samuel W. Glur quickly shared his findings with his colleagues - and in 1953, the Glycine Airman was born.
Glycine Airman Special, circa 1950 (Source: Horlogium @aptronym)
Originally powered by a self-winding mechanical movement, the Felsa 692, this 36 mm watch was a genuine technical achievement for its time.
Want to know how an automatic movement works? Check out our guide to mechanical and automatic watches.
What set it apart? An original GMT function combining a 24-hour graduated rotating bezel with a dial also marked on a 24-hour scale. The hour hand completed one full rotation of the dial every 24 hours - unlike standard watches, which run on a 12-hour cycle.
What truly sets the Glycine Airman apart from more recent GMT models is the absence of a dedicated GMT hand. The watch had only three hands - for hours, minutes, and seconds - and it was the rotating bezel that allowed you to read a second time zone. To do so, you unscrewed the crown at 4 o'clock to unlock the bezel, rotated it to the desired offset (using the "24" marker as a reference point), then checked which number on the bezel the hour hand was pointing to.
What makes this watch a true GMT watch isn't its set of hands - it's the 24-hour graduated bezel.
How Is the GMT Complication Useful When Traveling?
To better understand this, let's look at a concrete example: if you were in Basse-Terre at 17:00 and wanted to know the time in Paris (a +6h difference), you would align the "24" on the bezel with the 6 o'clock index on the dial. Result: the hour hand would point to 23:00, giving you the time in Paris. The hardest part was simply knowing (by memorizing or jotting down in a notebook) the exact time offsets between the different zones.
Shortly after this first innovation, in 1954, another iconic watch was born: the Rolex GMT-Master 6542, designed for pilots at Pan Am Airlines. This model would lay the groundwork for how modern GMT watches work.
Fitted with a two-tone bakelite bezel (a synthetic resin that was hugely popular at the time) in blue and red - a now-legendary color scheme nicknamed "Pepsi" by enthusiasts.
Rolex GMT-Master 6542, circa 1950 (Source: Rolex Magazine)
This Rolex had a 38 mm diameter, no crown guard yet, and featured a riveted Oyster bracelet along with radium-coated indices (a radioactive luminescent material). Most importantly, it introduced the use of a dedicated GMT hand, painted in bright red, allowing an instant read of a second time zone - a true step forward compared to the Glycine Airman released just one year earlier.
Rolex GMT-Master 6542 advertisement, circa 1950 (Source: Les Rhabilleurs)
Its operation relied on two readings: the main time via a hand rotating on a 12-hour scale, and the second time zone via the GMT hand completing one full rotation every 24 hours. This display method, which became the standard, offered a clarity that quickly won over airline pilots.
The Rolex GMT-Master 6542 came in several variants, including a rare model nicknamed "Albino" featuring a white dial, and even an all-yellow-gold version. Its fame would only grow further, thanks to the world of cinema.
Rolex GMT-Master 6542, circa 1950 (Source: Antiquorum)
In the film Goldfinger, released in 1965, it appears on the wrist of Pussy Galore, the iconic James Bond girl. The watch - stainless steel with an Oyster bracelet and Pepsi bezel - features prominently on screen, further cementing its iconic status.
Pussy Galore wearing a Rolex GMT-Master 6542 in Goldfinger, 1975 (Source: Le Petit Horloger)
A few years later, another version of the GMT-Master - reference 1675 - made its mark on the big screen. In the cult film Apocalypse Now (1979), Marlon Brando wore it on his wrist - but in a version he modified himself. To better suit his character, the actor removed the GMT bezel and swapped the steel bracelet for a black rubber strap designed to mimic lizard leather.
Rolex GMT-Master 1675 worn by Marlon Brando in Apocalypse Now (Source: InsideHook)
A rudimentary engraving was also added to the case back. Ironically, this deliberately unrecognizable version has become one of the most iconic watches in cinema history. In 2019, it was sold at auction by Christie's for the handsome sum of approximately five million euros.
Just 3 years later, in 1982, another Hollywood icon added his chapter to the story: Clint Eastwood. He appeared in the film Firefox wearing a Rolex GMT-Master 16753 on his wrist. This two-tone model in steel and yellow gold, fitted with a chocolate brown dial and a Jubilee bracelet, was part of the actor's personal collection.
Clint Eastwood wearing a Rolex GMT-Master 16753 (Source: Rolex Magazine)
He would go on to wear this model in several other films, including Tightrope (1984) and In the Line of Fire (1993). Since then, watch enthusiasts have given this Rolex reference the nicknames "Root Beer," "Dirty Harry," and "Clint Eastwood."
Pablo Picasso wearing a Rolex GMT-Master (Source: Rolex Magazine)
The GMT complication won over pilots and adventurers alike - but also artists. The painter Pablo Picasso was also a Rolex GMT-Master wearer, proudly sporting one in one of his most famous black-and-white portraits, dressed in a Native American headdress.
It's worth noting, however, that GMT long remained a niche complication. Few vintage models feature it, which makes them all the more sought after today. But with the renewed interest in technical watches, GMT is now more popular than ever.
Seiko 5 Sport GMT ref. SSK023K1
Today, many brands offer models with this function - and it's even possible to own an automatic GMT watch for well under 1 000 €. Something that would have been unthinkable just a few years ago. Plenty to satisfy both frequent travelers and watch enthusiasts alike.
GMT watches feature an additional hand specifically dedicated to displaying a second time zone, known as the "GMT hand." This hand is mounted on the same central axis as the standard hour, minute, and - depending on the model - seconds hands.
The 4 Hands of a GMT Watch
Watch brands consistently compete in their creativity when it comes to the GMT hand. Its shape is typically distinctive, and its contrasting color - red, orange, green, yellow, or even pink - makes it easy to spot at a glance. This pop of color isn't purely aesthetic: it also enhances overall legibility, especially for travelers on the go or professionals on the move.
GMT hands compatible with Seiko NH34 movement (Source: Lucius Atelier)
GMT watches are also recognizable by their 24-hour graduated scale. On some models, this scale is integrated directly into the dial - particularly on dressier watches.
GMT Watch, no GMT bezel, with graduation on the dial
On most sport-oriented pieces, however, it sits on a rotating bezel, often bidirectional. Some GMT watches even feature a double 24-hour graduation - one on the dial, one on the bezel.
To improve legibility on their GMT watches, many watchmakers opt for a two-tone bezel, making it easy to distinguish daytime hours from nighttime hours.
Rolex GMT Bezels (Source: Bob's Watches)
The iconic blue-and-red "Pepsi" combo, along with variants in black-and-blue, grey-and-black, and green-and-white, offers a virtually endless range of eye-catching configurations.
If you've been following this guide closely, you should already have a pretty good idea of how to read this type of watch.
Let's take a moment to recap what you'll find on a modern GMT watch with a 12-hour time display:
You'll notice that the GMT hand and the graduated bezel are the only two elements operating on a 24-hour cycle - which is exactly why they're always read together.
If your watch is set as follows:
You now have two time zones displayed simultaneously. To check the time in New York at any point during the day, simply find the position of your watch's GMT hand and see where it points on the bezel. Just be sure the bezel hasn't been accidentally rotated, as that could throw off your second time zone reading.
Did you know that your watch's GMT bezel can also let you read a third time zone?
Say you have family or clients in Finland, in Helsinki, and you always want to know what time it is there. From experience - or simply from doing your research - you know that Helsinki is 7 hours ahead of New York. Start by rotating your watch's GMT bezel to move its small triangle or "24" marker (depending on the model).
GMT bezel indicator to be moved
And don't forget: while your watch's bezel is graduated on a 24-hour scale, the dial runs on 12 hours. So instead of aligning the bezel triangle with the 7 o'clock index, you'll need to point it to 3:30. Once you've done that, leave everything as is - your watch is now set to display a third time zone.
That way, whenever you want to know the time in Helsinki, all you have to do is find the number on the bezel that your watch's GMT hand is pointing to.
The fact that the GMT bezel may have been rotated can allow you to display a third time zone, but it makes reading the second one less straightforward. To get around this, some watches use a double 24-hour graduation so you can read both the second and third time zones without any confusion.
GMT Watch with Two 24-Hour Graduations
Note: With their graduated bezels, some GMT watches can look a lot like dive watches. Just compare a Rolex GMT-Master with a Rolex Submariner - you don't need to be an expert to see just how many similarities there are.
Rolex Submariner 116610LN vs Rolex GMT-Master II 116710LN (Source: Everest Horology Products)
Some brands even lean into this ambiguity by offering professional dive watches with a GMT function - like the Omega Seamaster Diver 300M, the Longines HydroConquest, and the TAG Heuer Aquaracer, all available in versions featuring this coveted complication.
Understanding how a GMT watch works is one thing - knowing how to properly set one is another. And not all models are set the same way.
There are two main categories: "true GMT" watches (also called "traveller's GMT") and "office GMT" watches (also known as "caller GMT").
"True GMT" vs "Office GMT" Watch (Source: WatchCrunch @watchobsessed)
With everything covered in this guide, you may not become a master of time - but you're now fully equipped to understand, use, and appreciate the GMT complication, both in its technical dimension and in its historical and aesthetic subtleties.
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