Complications: The GMT Watch Explained

A watch is much more than just an accessory or a fashion statement. It’s a functional tool and a physical representation of the technological advancement of humanity as a whole. And if you don’t believe that, you simply haven’t done your research. Horology is a fascinating practice and deserves a tremendous amount of respect. Watches are astonishingly intricate, beautiful in their complexities, and something which we believe every single man should own in their lifetime.

But you shouldn’t just jump blindly into buying the first watch that catches your eye. Because, you see, there’s a whole world of alternative functionalities in the watch world, also known as complications. That’s right; any function outside of normal time-telling on any given wristwatch – whether it be as simple as a rotating bezel or as impossibly complex as a Tourbillon – falls into this category. And it is with these features, we hope to help you understand how they function. In particular, this article is meant to introduce you to the world of GMT watches, how they work, and what you might use them for in the real world.

History of the GMT

It might sound a little bit absurd, but the origins of the GMT watch – or at least the reason for their necessity – can actually be traced back as far as ancient Egypt. That’s because it was the ancient Egyptians who first divided the days into 24-hour increments by measuring the path of the sun and the stars across the sky. It is not, however, this invention in and of itself that gave rise to the GMT. That honor goes to another human invention that wouldn’t be brought into existence for thousands of years: air travel.

For centuries, the 24-hour system used by the Egyptians was tweaked, perfected, and spread around the world until all large human cultures used some version of it and, eventually, the exact same version across the board. But, because the Earth is round, that also meant that noon in one place could be literally any other time depending on the location around the globe. And it was hard to keep things straight. Then, in 1675, Greenwich Mean Time (AKA GMT) was established to help aid sailors at sea by giving them a stable reference point they could look to – namely, the local time in Greenwich, England (just southeast of London) at the Prime Meridian (Longitude 0).Pilots needed a means by which they could keep time in both the timezone they were leaving and in the one to which they were traveling. By 1884, it was adopted the world-round as the standard both by sea and on land.

Then, in 1879, a man by the name of Sir Sanford Fleming – a Scottish-born Canadian – introduced the idea of incremental timezones. He believed that, just as there are 24 hours in the day, so should there be 24 different equally-spaced timezones around the globe. Of course, that system – with slight variation – was also adopted around the world and we still use it today. This affected watch operation very little, as it would still take people days or even weeks to travel between timezones and wearers could adjust their watches accordingly. Then, in 1952, the first intercontinental jet flight from England to South Africa changed everything.

The establishment of commercial air travel gave people the ability to move great distances in a relatively short amount of time. Short enough, mind you, that we could switch from timezone to timezone within hours – rather than days or weeks. Especially for pilots, this made it difficult to keep track of the clock accurately. The idea of the GMT watch was born out of necessity and convention. You see, pilots needed a means by which they could keep time in both the timezone they were leaving and in the one to which they were traveling – without all the mess math can bring. So, air travel giant Pan Am approached legendary watch brand Rolex to ask for a solution. And, in 1954, the Rolex GMT-Master was born.

How GMT Watches Work

The functionality of a GMT watch from a user standpoint is quite simple. It works like this: a regular watch, generally, keeps 12-hour time. That means the hour hand of a watch will sweep around the watch face twice in any given day. In order to incorporate GMT-functionality, another hour hand is added to the dial – as well as a complication within the watch gears itself – that spins around the dial once per day, making it a 24-hour hand. Typically, this additional hand is arrow-shaped and colored differently from the normal 12-hour hand. Because hours and minutes do not change regardless of timezone, their position has no bearing on GMT functionality outside of their normal time-telling purpose.

But an additional hand is only one part of the equation. Because a normal watch dials only exhibits 12-hour increments (even if it has a secondary sub-dial with 13-24 numbers on it), another means by which the user can read the GMT hand is necessary. This can be found around the dial on the watch case itself. We mean, of course, the bezel. Similar to dive watches, GMTs use a rotating bezel with 24 incremental markings around the exterior to indicate the 24 hours in a day. When reading the GMT function on a watch, you’d refer to the number at which the colored arrow hand is pointing to on the bezel.So, when reading the GMT function on a watch, you’d refer to the number at which the colored arrow hand is pointing to on the bezel. Why does the bezel rotate, then? So you can choose your secondary timezone.

It works like this: If you were in Greenwich, England, the 0 position of your bezel (usually marked with an upside-down triangle) would point directly at 12 o’clock. For reference, let’s say it’s midnight. At midnight in Greenwich, the hour hand of your watch and the GMT hand will both point directly to the 12 o’clock marker and, by proxy, the 0 or 24 marker on the bezel. Surrounding timezones increase or decrease the hour by plus or minus 1, depending on whether you move east or west. So, using the same midnight example, moving one timezone east would count as +1 to GMT time – meaning it’s an hour later than in Greenwich. Thusly, you rotate your bezel one “click” counterclockwise, so that your hour hand points to midnight and your GMT hand points to 1 (or 1 a.m.). Similarly, if you move one timezone west, you’d be at -1 (or 11 p.m.) and would thusly need to rotate your bezel one “click” clockwise.

Every timezone around the world works in relation to GMT time, so you’d use the same method based on whatever plus or minus GMT time it is wherever you need to refer. So, setting your GMT watch is a 2-part process. First, you must set the bezel so that your watch reads GMT time, then you can add or subtract hours until your GMT hand points to the proper timezone time. You can also skip that first bit if you know how to read 24-hour military time and simply rotate your bezel until it points to the proper hour in whichever timezone you desire.

Real World Applications

Once you understand their purpose and how they function, it’s pretty easy to see that most of a GMT watch’s applications are related to travel. For instance, a pilot might want to know both the time in the timezone in which he took off and also the one in which he plans to land. Similarly, frequent travelers – especially with one specific recurring destination – might want to know what hour it is both where they’re headed and from where they came.

But there are also a couple of reasons you might want a GMT watch if you aren’t a traveler. For instance, if you work remotely and your job’s main hub is in another part of the country – like, say, a west-coast stock broker who needs to pay attention to the clock on Wall Street in New York – it’s pretty handy to be able to just glance at your watch.You’ll be better off depending upon a GMT watch to tell you the accurate time, rather than potentially making a costly mistake. Similarly, if you are one of the millions of people around the world with family in other countries, you could want to know the time wherever they might be, so as not to disturb them in the middle of the night or during dinner.

You might say that all of this can be done fairly easily without the use of a GMT watch. And that would be the truth. It is entirely possible to figure out alternate timezones relatively quickly with just a little brain math. But, as we know, humans are prone to making mistakes – especially under pressure. So, if you’re got a deadline to make or a time-sensitive phone call with someone across the pond, you’ll be better off depending upon a GMT watch to tell you the accurate time, rather than potentially making a costly mistake.

Victorinox 241648 Infantry GMT ($325)
Hamilton Jazzmaster GMT Auto ($1,275)
Rolex GMT-Master II ($7,740)

The Traveler’s Timepiece

Thankfully, with greater technological advancement comes more availability. Sure, the GMT is hardly the most cost-adding complication to be had, but it’s still somewhat out of the ordinary and, therefore, hasn’t always been easy to find or afford. But, since watches in general and their specialized varietals have become easier to build, they’ve also become more popular and, by proxy, more available. Now, you can find a killer GMT watch for just about any budget. So, whether you’re sitting coach on a fully-packed commuter plane or you’re riding shotgun in your own private jet, there’s a GMT wristwatch for you. The ones pictured here are some of our favorites.

The Chronograph Watch Explained

Maybe a multi-timezone watch isn’t the right thing for you or perhaps you more greatly value, say, stopwatch functionality. Well, then you might be interested in learning a little more about what exactly a chronograph watch is from our article explaining it.

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