Everything you need to know about GMT watches

The term GMT may seem barbaric at first glance, but it is actually very simple to understand and it represents a very important part of watchmaking history. A watch collector must have a GMT among all his toquants. Here is an article to familiarize you with this type of model so dear to watchmaking.

This complication has the particularity of displaying two or even three different time zones. Indeed, in addition to giving the local time, this very special timepiece offers the possibility of reading the time of a second time zone thanks to a fourth hand and a flange displaying the 24 hours of a day. Often very distinguishable from the first hour hand, the second time zone hand sports a color contrasting with the rest of the watch so you can spot it at a glance. But let’s not reveal too much right away and let’s get back to the history of so-called “GMT” watches and why they are so popular today.

The origin of the term “GMT”

To better understand this strange nickname, we must go back to the origins of the term GMT. It comes straight from the language of Shakespeare, meaning Greenwich Mean Time. Once translated literally and with a certain barbarity, this gives us: “Greenwich Mean Time”. We must actually see behind these three somewhat strange words, a technique for calculating time, i.e. mean solar time at the Greenwich meridian. It is the meridian which crosses the Royal Observatory of Greenwich, on the outskirts of London in the United Kingdom (we recommend this little detour, you will discover a magnificent park and a fabulous Maritime museum with the added bonus of a superb panoramic view on the surroundings of the world city).
Today, the Earth is divided into 24 time zones, but it should be noted that this was not always the case. For hundreds of years, each part of the globe had its own local time, based on the orientation of the sun. The arrival of railways and various technical advances allowing cross-border travel over much greater distances made these time zones a real headache that it was essential to simplify. It was then necessary to introduce uniform time zones across the world. Thus, Greenwich Mean Time served as a time reference around the world for most of the 20th century, before being replaced by Coordinated Universal Time (UTC) in 1972. Coming from the world of navigation, GMT enabled by the creation of an arbitrary border (the meridian) to divide our planet from East to West in order to read geographic longitudes.

Note that our good old GMT is based on the Earth's rotation while UTC is based on international atomic time. The calculation of time is therefore much less precise with a GMT type evaluation technique. But don't worry, today when we talk about GMT complication, there is no link with the precision of the watches. This term has simply remained in common watchmaking language, to designate these very practical watches, but the watchmaking rigor comes from the movement! Be careful though, the term GMT is not universally adopted by watch companies either. Indeed, it is not uncommon to see brands like SINN (German company) use the UTC acronym instead of GMT.
GMT watches

Now that we have gone back in time and better understood where the term GMT came from, it is necessary to tell you about GMT watches and their much appreciated complication. The wearer of a watch of this type can know the exact time in two time zones as specified in the introduction to the article. Reading the two time zones is done on the same dial and is made easier by the play of colors on the hand and the flange. The fourth hand functions like that of a 24-hour watch, pointing to the flange dotted with all the hours of a day. It is independently adjustable directly via the crown although it can also be linked to the hour hand.

The GMT watch has therefore established itself in the watchmaking world as the favorite accessory of any good globetrotter. Indeed, wherever he is, the seasoned traveler with a GMT will be able to know the time of his country of origin and the time of his host country at a glance. It is for this precise purpose that the first GMT watch was created in the aftermath of the Second World War. At this time, international travel was increasing and it became essential for pilots to know the exact takeoff and landing time of their flight without cluttering the view from their cockpit with several time indicators. Frequent travelers will let themselves be more and more tempted by this complication which is so useful during their epic journeys: knowing the exact time at home to call a family they miss without waking them up, sending an email for business without appearing impolite, not be late for a visit or an appointment, because you forgot to set your watch to the correct time zone... In short, with such a complication, two time zones on the wrist, it limits the risk of problems and greatly facilitates the life. And good god, isn't it magnificent to have four hands on the same dial?
We very often recognize a GMT thanks to its famous two-tone bezels and for good reason! They were created to make it easier to distinguish between morning and afternoon by reading the time in the second time zone. They gave their nicknames to iconic watches which we will talk about below, such as the “Pepsi” or the “Coca-Cola”.

What about the third time zone?
If your GMT watch has a 24-hour rotating bezel, you can even use it to display a third time zone. Originally, it was an orientation aid for the GMT hand. However, with practice, you will quickly get used to reading it without the scope. Once you have mastered reading it, you can move the bezel to indicate a third time zone.

HERE ARE SOME ADVANTAGES OF OWNING A WATCH WITH GMT FUNCTION

You will have understood, if you are a frequent traveler, this function allows you to keep a nostalgic eye on the time at home and to understand why you are completely jetlag with the second time zone!
But here is a summary of what you can expect from your GMT:
The two-tone highlight displaying the 24 hours of the day allows you to distinguish morning from afternoon.

• The GMT brings real added value to your watch from a technical point of view. It is indeed an interesting, complex and beautiful complication to observe in motion. If you want more information on this subject, take a detour to our article about the C125 from Soprod, a little gem…
• An elegant and original accessory thanks to its varied dial colors which often catch the eye of the passer-by.
• If you're a real MacGyver, GMT watches can be used as a compass (if you really use it that way, we'd like a tutorial from Charlie Paris).

OUR SELECTION OF ICONIC GMTs

• How can we talk about GMT without talking about Rolex? The crown brand having bought the Bucherer reseller on August 25, 2023, was from the start the companion of the greatest professionals: divers (Submariner), scientists (Oyster Perpetual Milgauss), but also pilots! Indeed, the Rolex Oyster Perpetual GMT-Master was presented to the public in 1954 and was developed following a request from Pan Am (Pan American World Airways) which wanted a watch intended for its airline pilots on flights transcontinental. On the Rolex GMT-Master II launched in 1983 with caliber 3085, the minute hand is set at the same time as the GMT hand. The local hour hand can subsequently be adjusted independently.
• How can we not talk about Omega, with its caliber 1128, for example in the Seamaster 300 M GMT. Without forgetting, in its Seamaster collection, the introduction by Omega of an extraordinary GMT, making an impression thanks to its touches of orange and a dial which plunges us into the abysses of the ocean with its intense blue. Omega also has in-house feats in store for us, notably the Omega Planet Ocean 600 M GMT which houses the caliber 8605 with Co-Axial escapement.
• Breitling also offers its own collection of GMT watches with the Avenger II GMT, which captivates with its striking riders and satin-finished stainless steel bezel.
• With the Luminor GMT, the Italian luxury brand Panerai gives one of its best-known collections a second time zone at 9 a.m.
• Finally, we had to talk about our creation. The Concordia GMT from Charlie Paris, here is a GMT with charm! Both sporty and refined, the Concordia GMT accompanies the most experienced adventurers but also everyday urban explorers. This watch meets all the specifications for GMT watches... but also for divers. Indeed, it is equipped with a unidirectional rotating bezel with a luminescent marker at noon. Its screw-down crown allows it to reach 300m of water resistance and a red insert lets you know if the crown is open or not. The “barrel” shape of the crown allows for much simpler handling and its blue outline perfectly recalls the bezel. A two-tone flange is inserted around the dial allowing smooth and rapid reading of the second time zone with the fourth hand distinguishing itself from the other three by a different color. Its lightness for a 40mm diameter diving watch makes it very pleasant to wear in everyday life. It can also be adorned with a steel, nylon or even leather bracelet in just a few seconds with its flash pump system! In short, it is a magnificent watch made in Paris which will delight more than one person.

Thus, the GMT will have made its mark and continues to make timepiece lovers dream. It is first of all to respond to a very specific technical problem that it appears. Then it became popular on the wrists of travelers around the world. Eventually becoming institutionalized as an essential complication in the world of watchmaking. This was the story of GMT.