Complications: GMT and World Time

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Whether you’re a frequent traveler or just have regular communication with people in different time zones, knowing the time in more than one place can often be a very useful thing to have on your watch. In this installment of Complications, I’m taking a look at the GMT complication—how and when it first came about, a few different variations of display and usage, and some of the mechanical movements often used.

GMT is short for Greenwich Mean Time and it’s the average (or mean) time that the sun crosses the Greenwich meridian—“average” because the exact time this occurs can vary by up to 16 minutes throughout the year.

Royal Observatory, Greenwich.

The first GMT watches were intended to show GMT time in addition to local time, but for most people, the GMT hand is likely to be used as a reference to home time instead. With two times to display, the local time is displayed against the usual 12-hour dial with an additional GMT hour hand completing a rotation of the dial once every 24 hours and referenced against a 24-hour scale either on the bezel or dial itself. A watch with a 24-hour scale on both the dial and the bezel is capable of tracking three time zones at once: one against the regular hour hand and two—in 24-hour notations—against the GMT hand.

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First, it is worth noting that Glycine unveiled the Airman in 1953. At that time, the standard for the international civil time was GMT, although this was replaced by Coordinated Universal Time (UTC) in the 1970s. The Airman was a low-cost development from the brand that tracked time on a 24-hour scale, with an additional 24-hour bezel for a second time zone and GMT time. There was no second GMT hand. Rolex then introduced its GMT watch in 1954, working with Pan American Airways to provide a watch capable of keeping track of local and GMT time, a necessity for pilots crossing many time zones on long-haul flights.

Rolex ref. 6542.

The Rolex GMT Master, ref 6542, used the caliber 1036 movement which had a GMT hand slaved to the hour hand—that is, the hands could not be set separately to show separate times. Setting the second time zone was done by rotating the bezel. In a world of lavish complications, it was a relatively simple solution to run an extra hand geared at half the speed of the existing hour hand. But this addition paired with a rotating bezel (the bezel on the original GMT master was a simple friction bezel able to move in either direction and with no clicks) proved incredibly useful and the concept is still popular today.

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It was only with the introduction of the GMT Master II in 1983 that the Rolex gained a quick-set hour hand, allowing the GMT and hour hands to be set independently, and this is where several variations occur. In the GMT Master II’s caliber 3186 movement, among others, the minute hand is set along with the GMT hour hand, and the local hour hand is set independently and jumps at one-hour increments. Other familiar movements operating in this way include the Omega caliber 1128 as seen in the Seamaster 300 GMT “Great White,” and Grand Seiko’s Hi-Beat 9S86 movement used in the stunning SBJG005 and its iterations.

Grand Seiko SBGJ021 (a later limited edition of the SBJG005).

The other alternative is for the GMT hand to be independent of all others and to jump one hour at a time. This approach is commonly seen in watches utilizing the ETA 2893-2 GMT movement. If you are likely to need to change your local time fairly regularly while keeping the reference 24-hour time unchanged, then the 2893-2 isn’t the ideal means for achieving that goal. An independent local hour hand will give one the ability to move the local time forward or backward at one-hour increments without hacking the second time or needing to calibrate the minute hand.

Most GMT complications are distinguished by the use of a large arrow hand, often in a different color to the other hands, to distinguish GMT or home time. One of my favorite affordable GMT watches is the Citizen Nighthawk, which uses a hand extending both ways from the center, and a different color airplane at each tip. Each tip then extends a slightly different distance from the center and reads against the appropriate scale printed near the middle of the dial—one for 1-12 hours and the other for 13 to 24 hours.

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If you aren’t looking to track time zones stretching across the globe and a 12-hour display provides the functionality you need, dual time watches are worth taking a looking at. These are watches that have an hour and minute hand on a sub-dial as well as centrally; each one is set independently. While there is a lot of choice on the market, one of the coolest is Oris’ Big Crown ProPilot Worldtimer where the bezel is used to move the central hour hand forward or backward an hour at a time.Speaking of which, the world time complication, a watch which displays the time for cities across the globe concurrently on the dial, may seem like an obvious extension of the premise of a GMT watch, but the first world time watches were created decades earlier. Louis Cottier is credited as the creator of the world time complication and worked with Vacheron Constantin on a pocket watch featuring the names of cities around the outer ring, and a rotating 24-hour ring which would display the current time in each of those cities. Cottier later worked with many other famous names in watchmaking and produced the first world time wristwatch with Patek Philippe, which was the first dual time watch to use a single movement, resolving any synchronization issues from having the local and 24-hour times running from different movements.

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Most world time watches will feature a disc marked with 1-24 that rotates over a 24-hour period. This is measured against a second disc through which the wearer sets their home time. With the normal 12-hour display in the center of the dial set to show local time, the time in 24-hour notations can be read against all time zones shown on the dial. Most watches with this complication will choose to show one major city in each time zone, but some such as the Vacheron Constantin Overseas World Time will show 37 time zones, including those such as New Delhi, which is five-and-a-half-hours ahead of GMT.Nomos and Christopher Ward both offer watches labeled as world timers, although neither displays the time across all time zones at once. The Nomos Weltzeit lets the wearer adjust which time zone corresponds to their home time, and once this is set the pusher at two o’clock is used to rotate the disc on the right-hand side of the dial to show a different time zone. As the time zone jumps one place, the hour hand jumps with it. Christopher Ward’s C900 opts to display both local time and a second time zone in a 24-hour notation on the same dial, while the adjustment of the time zone (airport code) displayed in the window at the top of the dial jumps the red hand (for the second time zone) and the accompanying red dot indicator on the world map.

Though fairly simple in concept and often in execution, both GMT and world time complications offer a real benefit to frequent travelers. Perhaps due to the simplicity of the information being displayed, the GMT remains relatively unchanged since its introduction in wristwatches in the 1950s, but the world timer will likely encourage more interesting developments in the future.

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Brad stumbled into the watch world in 2011 and has been falling down the rabbit hole ever since. Based in London, Brad's interests lie in anything that ticks, sweeps or hums and is slightly off the beaten track.
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