How GMT Watches Work: Our FAQ on Watches for Travelers

How GMT Watches Work: Our FAQ on Watches for Travelers

GMT watches, and other types of watches with useful complications for travelers, are enjoying a surge of popularity these days, with watchmakers large and small stepping up to produce travel watches with both user-friendly mechanics and attractive design, at a variety of price points. Yet, if you’re new to the watch game, you still might be a bit curious or even confused about how GMT watches work, how to read and set them, and how one style differs from another. In this feature, we attempt to address all the pertinent questions you may want answered before purchasing a GMT or any style of watch with the ability to show multiple time zones.

What is a GMT watch?

Longines Spirit Zulu Time

GMT is the abbreviation for “Greenwich Mean Time,” the system of world timekeeping based on the calculation of mean solar time from the Royal Observatory in Greenwich, London. Established in 1884 at the International Meridian Conference, the Prime Meridian was conceived as a straight line running from the North Pole to the South Pole directly through Greenwich, serving as the point of zero degrees longitude from which 24 separate time zones divide the Earth: the Eastern Time Zone of the United States, for example, is designated as GMT -5 (i.e., five hours west of Greenwich, which is GMT 0). A GMT watch is essentially a timekeeper designed in that same utilitarian spirit, allowing its wearer to read the time in at least two time zones simultaneously. Many such watches actually use the initials “GMT” in their model names, while others use terms like “Zulu Time” (descended from military jargon for the Greenwich Prime Meridian, as in the Longines Spirit Zulu Time watch pictured above), “UTC” (for Universal Coordinated Time, the successor to Greenwich Mean Time), or the more descriptive “Dual Time.” 

How do you read the dial of a GMT watch?

Tudor Black Bay GMT

The most popular and recognizable type of GMT watch combines a standard 12-hour dial with a 24-hour bezel, the latter often but not always bisected into two colored sectors — one repping the daylight or AM hours, the other denoting the nighttime or PM hours. The dial has two hour hands; One is for the local time, which points to the hour on the 12 markers and usually matches the style of the minute hand. This hand makes the traditional two rotations around the dial every 24 hours. The additional hand, which makes only one rotation every 24 hours, is usually executed in a slightly different style or color from the main handset and points to a different time on the bezel’s 24-hour scale. Once both hands are set, all that’s required to quickly read both times at a glance is a working knowledge of 24-hour time and a bit of simple math. On the Tudor Black Bay dial pictured above, the local time is 10:10; the “home time” or “reference time” is 15:10 hours GMT, or 3:10 PM. 

What was the first GMT watch?

Watchmakers have been coming up with clever ways to indicate the time in more than one location at least since the world adopted the concept of time zones. As early as 1908, Longines developed a pocket watch for a client in the Ottoman Empire (today’s country of Turkey) that used two distinct hands to display the time in both that nation and in France simultaneously. In 1931, legendary watchmaker Louis Cottier developed the first “universal time” watch movement, with a rotating bezel depicting international cities to represent the time zones, which was used by Patek Philippe and Vacheron Constantin. These timepieces were the forerunners of many of today’s world-time watches, which are described in a bit more detail later on. 

Rolex GMT-Master II

The template for the GMT watch as we know it today is the original Rolex GMT-Master Ref. 6542, developed in a partnership between Rolex and the aviators of Pan American Airlines, at the time one of the U.S.A. 's leading commercial carriers, and launched in 1954. As I explore in much more detail here, the watch’s raison d’être was to allow pilots on long-haul international flights to easily keep track of the time in both their departure city and their destination anywhere in the world. The watch was the first to establish the now-familiar style described above, with the bicolor 24-hour bezel and additional arrow-pointed hour hand. The red-and-blue bezel sectors of the first GMT-Master famously moved collectors to nickname the model the “Pepsi,” and kicked off a number of other bicolor bezels in subsequent nicknamed models, like the red-and-black “Coke,” blue-and-black “Batman,” and brown-and-black “Root Beer.” As of the Ref. 16760, launched in 1983, the GMT-Master became a “true” GMT, with its GMT hand decoupled from the main hour hand to allow for independent setting of the former, and has been known ever since as the GMT-Master II.

What is the difference between an “office” and “true” GMT?

Seiko 5 Sports GMTGMT watches mostly fall into one of these two categories: the former term refers to a watch whose 24-hour hand is independently adjustable, while the latter describes a watch with the opposite functionality, i.e. the 12-hour local-time hand can be independently adjusted. Each type finds its most useful application in a specific setting from which its nickname is derived: the “office” type (like the Seiko 5 Sports GMT above, and also referred to by the somewhat outdated term “caller”) is better suited for someone like an executive who is mostly stationary in his or her own work but connects regularly with international clients or colleagues in different time zones and thus needs to easily change the second-time-zone reading on the dial. The “true” (also called “traveler”) style of watch is better for frequent travelers, who need to regularly and easily change their local time while keeping their home time consistent.

How many time zones can be displayed on a GMT?

Tudor Black Bay ProA GMT watch is designed to display the time in a minimum of two time zones, one of which would theoretically be the wearer’s local time zone, but many can actually allow a reading of three time zones at once. It all depends on whether or not the 24-hour scale is fixed (as in the Tudor Black Bay Pro above) or rotatable. With the former style of scale, the only two time zones that can be read are the one indicated by the main hour hand on the 12-hour scale and another indicated by the additional “GMT hand” on the 24-hour scale. However, if the latter scale is on a rotating bezel, the wearer can simply turn it so the number on the scale referring to a third city’s time zone (i.e. Tokyo at GMT +9) aligns with the GMT hand for a reading of the hour there. 

What’s the difference between a GMT and a World Timer?

Omega Aqua Terra Worldtimer

While a GMT watch allows for a view of two (in some cases three) time zones, a world time watch, like the Omega Aqua Terra Worldtimer above, is designed to display the time in all 24 of the world’s time zones at once. Usually this style of watch follows the template established by Louis Cottier and Patek Philippe in the 1930s: it combines a 24-hour scale that rotates around the dial, in concert with the hour hand, once a day, with an outer bezel inscribed with the names of 24 world cities, each representing one of the major time zones. The wearer can set this “city ring” to the local time while traveling and can read the time in any other time zone by seeing where the cities align along the 24-hour scale. We showcase some of our favorite world time watches here.

What are the other types of dual-time watch?

A. Lange & Söhne Lange 1 Time Zone

The traditional GMT, with 24-hour bezel and second hour hand, has settled solidly into its position as the most popular style of dual-time watch, but some watchmakers have come up with other dial designs, and correspondingly, other types of movements, to track the time in multiple zones. Montblanc developed an intriguing visual style for its 1858 Geosphere series, whose dials feature a unique dual-time display with two 3D globes on the dial, one for each hemisphere, along with a 24-hour scale, a day-night indicator, and a date disk. German high-horology house A. Lange & Söhne cleverly tweaked the asymmetrical dial layout of its flagship Lange 1 model to create the Lange 1 Time Zone (above) in 2005: the main (i.e. local) time display remains on the large subdial at 9 o’clock while the smaller 5 o’clock subdial, rather than hosting the running seconds, displays a second time zone on two hands in a 12-hour format. A switchable city ring occupies the dial’s periphery, activated by a synchronization mechanism that enables the wearer to “swap” between the time zones indicated on the two subdials.

Jaeger-LeCoultre Reverso Tribute Duoface

Jaeger-LeCoultre has used the aesthetic versatility of its swiveling-case Reverso model to create its own version of a dual-time display in the Reverso Tribute Duoface. The watch’s main, front dial shows the local time while its back dial (above) hosts a figure eight of overlapping subdials, the larger one displaying the time in a second time zone, while the smaller one displays the local time in 24-hour format along with a day-night display. Patek Philippe, a longtime pioneer in multiple-time-zone watches, recently introduced the Calatrava 24 Hour Display Travel Time, which features only a 24-hour track (rather than a 12-hour track and a 24-hour bezel), a local-time hour hand that makes one rotation around the dial per day, and a skeletonized GMT hand that points to the same 24-hour scale; the indication of 12 noon at 12 o’clock and 12 midnight at 6 o’clock makes for even more simplicity in reading the time, dispensing with the need for a day/night indicator. 

How much will I pay for a GMT watch?

Bulova Wilton GMT

Fortunately for newer watch connoisseurs and those with more modest budgets, the GMT complication has become a lot more accessible at the entry-level end of the market in recent years, even in the very coveted mechanical segment. Japanese mass-market giant Seiko added a GMT to its Seiko 5 Sports collection in 2022, powered by its in-house automatic Caliber 4R34 and available in several striking dial-and-bezel combinations, priced under $500. For just about $100 more, Bulova offers its recently released Wilton GMT (above), which is not only a “true” GMT at an almost unbelievable price point (powered by another Japanese-made, self-winding mechanical movement, the Miyota Caliber 9075); its Roman numerals and textured world-map dial elevate it to a decidedly luxurious aesthetic.

Mido Ocean Star GMT

If your sights are set on a watch with a Swiss-made movement, you can still find very enticing offerings from brands like Zodiac, whose Super Sea Wolf GMT Automatic boasts an automatic Soprod Caliber and a classical vintage diver look and retails for around $1,600; and Mido, which squeezes both a 24-hour GMT scale and a 60-minute rotating diver’s bezel on its Ocean Star GMT model (above) for just under $1,300. Prices generally rise from there as you ascend into more brand prestige and high-end finishing; the Longines Spirit Zulu Time starts at just over $3,000 in its 39mm steel version; Tudor’s Black Bay GMT starts just shy of $4,000 on a fabric strap while the slightly less sophisticated Black Bay Pro can be had for $3,825. The O.G. Rolex GMT-Master II (below), as one might expect, will run you quite a bit more, starting around $15,000 at retail and marked up substantially from that MSRP on the secondary market, where you’re much more likely to find one. Of course, you can always peruse our list of 25 of the best GMT watches on the market today to expand both your horizons and your choices. 

Rolex GMT-Master II Pepsi - wrist

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