What Is a GMT Watch, and Do You Actually Need One?

Vaiana Express | Updated August 2026 | 15 min read

A GMT watch does one specific thing a normal watch can't: track a second time zone without any guesswork. The Revue Thommen GMT Diver 17572.2138 does it with a dedicated 24-hour hand and a bi-directional bezel that can track a third zone on top of that — genuinely useful, not just a novelty complication. Here's what a GMT actually does, who needs one, and how this specific watch handles it.

What Is a GMT Watch?

A GMT watch adds a fourth hand to the standard hour/minute/second setup — one that makes a full rotation every 24 hours instead of every 12. That hand points to a separate 24-hour scale, usually printed on the bezel, letting you read a second time zone at a glance without doing any mental math.

The name comes from Greenwich Mean Time, the original reference point pilots and navigators used before time zones were standardized globally. The complication was originally developed for airline pilots who needed to track home-base time while flying through multiple zones — a direct, practical response to a real operational problem, not a marketing invention.

Why This Connects to Revue Thommen Specifically

This isn't a random complication for Revue Thommen to offer. The brand's own history runs directly through aviation instrumentation — from 1936 to 1943, it held a formal contract to build cockpit instruments for the Swiss Air Force, including altimeters and airspeed indicators. A GMT function is a natural extension of that same problem-solving lineage: instruments built to answer a specific, practical question (what time is it, really, when you're moving through the sky) rather than complications added purely for visual interest. For the full story, see our brand history guide.

GMT vs. Other Multi-Time-Zone Approaches

Of these, a true GMT like the 17572.2138 tends to hit the best balance for a mechanical watch: genuinely useful function, without the dial clutter of a full world-timer complication.

A Brief History of the Complication

The GMT complication as we know it today traces back to the early era of commercial jet travel in the 1950s. Pan Am pilots flying long-haul international routes needed a reliable way to track home-base time (usually GMT itself, for coordinating with ground crews and schedules) while operating on local time at their destination. The dual-hand solution — a normal 12-hour display plus an independent 24-hour hand — became the standard answer, and it stuck around long after paper flight logs gave way to digital systems, because it's simply a genuinely useful way to read two time zones at a glance.

What started as pilot equipment became a broader travel and business standard over the following decades, as international business travel grew and the same problem — needing to track two time zones without a phone or a second watch — applied well beyond the cockpit. That's the same practical logic behind the GMT Diver: it's function borrowed from aviation, applied to a watch built for everyday wear.

The Movement Inside

Revue Thommen's GMT models use either the ETA 2893-2 or Sellita SW330-1 caliber, depending on production batch — both genuine Swiss automatic movements built specifically with true GMT functionality, meaning the 24-hour hand adjusts independently via the crown rather than being mechanically linked to the main hour hand. That independent adjustment is what makes quick time-zone changes possible without disturbing your local time setting. Both movements offer roughly 42 hours of power reserve and the same accuracy standard (~±15 seconds/day when serviced) as the three-hand movements used elsewhere in the collection.

GMT vs. World Timer vs. Dual Time

GMT isn't the only way a watch can display multiple time zones — it's worth knowing how it compares to the alternatives you'll see on other watches.

For most people who travel between a small handful of regular destinations — say, home and one or two client or family locations — a true GMT like this one hits the practical sweet spot: more useful than a simple dual-time subdial, without the visual complexity of a full world timer you'll rarely use to its full extent.

Who Actually Needs One

A GMT complication is genuinely useful, not just a spec-sheet flex, for a specific set of people:

• Frequent international travelers who want to track home time without doing math at 2am in an unfamiliar hotel room
• Remote workers coordinating across time zones — knowing what time it is for a colleague or client at a glance, without pulling out a phone
• Pilots and aviation enthusiasts, given the complication's origins and Revue Thommen's own instrument-making history
• Collectors who want function, not just aesthetics — a GMT is one of the few complications that's genuinely used daily rather than admired occasionally

If none of that applies to you, a GMT is still a legitimate style choice — but it's worth knowing you're paying for a complication you may not use, versus a model like the Diver Green Dial that puts that value into finish and materials instead.

GMT Diver 17572.2138

42mm, 13.5mm Thick · 24-Hour GMT Hand · Bi-Directional 24H Bezel · 300m Water Resistance

~$3,000

The 17572.2138 pairs a black dial with a two-tone green-and-black bezel, and the red-tipped GMT hand stands out clearly against both. Underneath, it carries the same core spec sheet as the rest of the Revue Thommen dive lineup: genuine Swiss automatic movement, 300m water resistance, sapphire crystal, and a screw-down crown.

What sets it apart is the bezel itself. Unlike the standard 120-click dive bezel on the other models, the GMT's bezel rotates bi-directionally and is marked with a full 24-hour scale — meaning you can track a third time zone by rotating it to match, on top of the two the hands already give you. The case stays a wearable 13.5mm thick despite the added complication, so it doesn't feel bulkier than the standard Diver on the wrist.

The movement inside is a GMT-specific Swiss automatic caliber — typically an ETA 2893-2 or Sellita SW330-1 in this class of watch — built around a true independently-adjustable GMT hand. That's a meaningful distinction from cheaper "office GMT" watches, where the GMT hand can only be set together with the main hour hand rather than adjusted on its own. On this watch, you can change the GMT hand's zone without disturbing your correctly-set local time at all.

How the GMT Diver Compares to the Rest of the Lineup

The GMT sits at the top of the price range in the lineup, but for the right buyer — someone who'll actually use the second time zone regularly — it's genuinely doing more work day-to-day than either the chronograph or the standard three-hand model.

Shop the GMT Diver 17572.2138 →

How to Use the GMT Function

Using the GMT complication is simpler than it looks once you've done it once:

Once set, the GMT hand keeps running independently — you don't need to reset it each time you check the time, only when you actually change which second zone you're tracking (for example, after landing in a new country).

A Real-World Example

Say you live on the East Coast and regularly work with a team in London. Set your main hands to local East Coast time as usual. Set the GMT hand to London time (typically 5 hours ahead). Now, at a glance, you can see both times without doing any math — useful for knowing whether it's reasonable to send a message, or when a meeting actually lands on their calendar.

If you then fly to a third location — say, a work trip to Tokyo — you can rotate the bezel to add Tokyo time as your third reference point, while your GMT hand keeps quietly tracking London and your main hands get reset to Tokyo local time for the trip. That's the actual value of the bezel: it's not fixed to any one zone, so it flexes to whatever you need tracked at the moment.

Common Setup Mistakes

• Confusing AM/PM on the 24-hour scale — since the GMT hand only goes around once every 24 hours (not twice, like the hour hand), make sure you're reading the correct half of the scale for the zone you're tracking.
• Forgetting to reset after long trips — if you don't use the GMT function regularly, it's easy to leave it set to an old zone. Get in the habit of checking it against a phone when you land somewhere new.
• Adjusting the crown in the wrong position — GMT hands are typically set from a different crown position than the main hour hand. Check your watch's specific setting instructions rather than assuming it works exactly like a standard three-hand watch.

Styling & Everyday Wear

Despite the added complication, the GMT Diver wears close to the standard Diver models — the 13.5mm case thickness keeps it from feeling bulky, and the black dial with green-and-black bezel reads as a legitimate everyday watch rather than a pilot's tool piece that only makes sense mid-flight.

• For business travel: the stainless bracelet and relatively restrained two-tone bezel keep it appropriate for client meetings and business settings, not just airports.
• For everyday wear at home: even if you're not actively tracking a second zone that day, the watch functions perfectly well as a standard three-hand diver — the GMT hand simply sits at your set reference time until you need it.
• Setting convention: many owners set the GMT hand to home time permanently and adjust only the main hour hand when they actually travel — that way you always have "home" one glance away, no matter where the main hands are set.

Frequently Asked Questions