As you probably know, a GMT watch is capable of keeping track of two or three timezones at the same time. That is achieved by having an extra hour hand in addition to the second, hour, and minute hands usually found on most watches. Whilst the hour hand takes 12 hours for one lap of the dial, the fourth hand takes 24 hours for one lap. By adding a rotating bezel to the watch, three timezones can be tracked at the same time.
There are several design interpretations of the GMT time-keeping concept, and before we discuss the two types of GMT movements, let’s look at a bit of history.
In the 1950s intercontinental flights became available, and suddenly an Atlantic crossing took hours and not days. That meant travelling through multiple timezones and pilots needed to track time at home, time at destination, and also time at the current location. This was obviously long before computer technology made such information readily available, hence the need for a mechanical device that could provide the exact facts about time.
The first GMT watch to allow for dual timezone timekeeping was the stunning Glycine Airman, which has two 24-hour hands, a minute hand and a second hand. Furthermore it had a rotating 24-hour bezel which could be regulated by unscrewing the second crown located at 4 o’clock. There you go - three timezones at the same time!
It was however not Glycine that gave GMT watches their wider appeal. Pan Am were the pioneers of long distance flights and they had a natural requirement for watches that could provide their pilots with crucial information about time. Rolex was approached and in 1954 they answered the call with the GMT-Master - a now iconic watch which is probably the first thing you think about if you hear the word ‘GMT’. Unlike the Airman, the GMT-Master had a 12-hour hand and a 24-hour hand, and you didn’t need to unlock the rotating bezel - it simply moved bi-directionally in one-hour increments.
Since the introduction of the Rolex GMT-Master, which is visually almost identical to the Submariner (probably not a coincidence), it has been the symbol of wanderlust and the good life, jetting across multiple timezones. Most major watch brands have since embraced the GMT concept and offered their take on a multi-time zone watch. It is however Rolex that leads the way, and over the years the GMT-Master has evolved both technically and visually, and can be had in various materials and with various bezel colours.
How does it work?
To understand GMT, you need to know about Coordinated Universal Time.
Coordinated Universal Time or UTC as it is illogically shortened, is the primary time standard by which the world regulates clocks and time. It is within about one second of mean solar time at 0° longitude and is not adjusted for daylight saving time. It is effectively a successor to Greenwich Mean Time (GMT) . All airborne vessels use UTC, so onboard a plane the time reference is always the same, regardless where in the world the plane is.
Many movement manufacturers make a GMT movement, and you can have both mechanical and quartz regulated variations. Overall there are two different types of GMT movements:
- The Traveller’s GMT
- The Caller GMT
The Traveller’s GMT movement
As the name suggests it is the superior solution for frequent travellers who travel across time zones and need to adjust their watches often.
A watch based on a Traveller’s GMT movement displays the time centrally with local hours and minutes and date. There is also a 24-hour hand so visually there is no difference between the two GMT movements. A watch can be equipped with either, but you would not know which one of the two it is until you rotate the crown. The big difference between the two is that the Traveller’s GMT allows you to turn the 12-hour hand in both directions in one-hour increments. Why is that smart you wonder?
Here is an example:
Let’s say you are based in London, and you board a flight to New York at 9pm in the evening of the 6th of January.
At this point the 24-hour hand points to 9pm (or 2100 hours) and the 12-hour hand also says 9 o’clock. The date window indicates that it is January 6th. When you arrive 6 hours later, the time according to your watch is 3am and the date now says January 7th. As New York is GMT -5 hours, you adjust the 12-hour hand by 5 hours by pulling out the crown to its second position, making it 10 o’clock local time. As you adjust the hour hand the Traveller’s GMT movement will also adjust the date back to the 6th of January, which it still is for 2 more hours in New York.
The result is that the date is correct, the time according to the 12-hour hand is 10pm local time, and the 24-hour hand points at 3am, which is the time in London where you just arrived from.
Watches with a Traveller’s GMT movement onboard, like the Rolex GMT-Master II, typically cost from £3,000 and upwards.
The Caller GMT movement
The Caller GMT movement (sometimes referred to as the Office GMT) is ideal for people who work in an international environment, with contacts located across multiple timezones. In essence the Office GMT is a standard 3-hand movement with a 4th hand added. The latter takes 24 hours to lap the dial.
The Caller GMT makes the assumption, that you are spending most of your time in one timezone, but you want to keep track of two additional timezones. For that purpose you can adjust the 24-hour hand independently, and set the it to the timezone you need to track. So let’s assume you are in London and the time is 12 noon. Your colleagues are based in San Francisco, which is GMT -8 hours. That makes it 4am local time, and you now adjust the 24-hour hand to 0400 hours. There is also a team in New York that you like to track, and as they are in the GMT -5 timezone, you turn the bezel anti-clockwise by 3 hours, and voila - you can now see the time in London, New York and San Francisco at a glance.
When you travel with a Caller GMT movement based watch, you need a different approach to the example used above in the Traveller’s GMT description. You would simply leave the 12-hour hand alone and let it show London time during your stay in New York, and then adjust the 24 hour hand to reflect the time on location, ie the New York time. Or if you are staying for a longer period, do it the other way around.
The Caller GMT movement is not as complicated as the Traveller’s GMT and that is reflected in the price. You can assume that watches below £3,000 have a Caller GMT movement onboard. Popular automatic GMT movements like the ETA 2893-2, Seiko NH34, or the Sellita SW330-1 are all Caller GMT movements.
So which one should you choose? It is really a matter of your budget. If you have less than £3,000 to spend, and you want an automatic GMT watch, the decision has already been made for you. Visually there is no difference - you cannot spot one from the other, and the ability to track three time zones, one way or another, is available with both types of movement. In a perfect world you would pick a Traveller’s GMT, but the difference is insignificant, and there is a perfectly good work-around available if you find yourself travelling a lot with a Caller GMT based watch.
Enoksen and GMT
It is time for the introduction of the first Enoksen GMT watch. We have been on the lookout for a suitable movement for years without being able to find one that is made by a reputable company, is automatic, and is affordable. With the introduction of the Seiko NH34, the search is over. This new movement is based on the workhorse which is the NH35 - a movement that we have been using the last 5 years, and which we have found to be both ultra reliable and easy to adjust.
Say hello to Roam E07/A - the first GMT watch from Enoksen. It is based on the popular 40.8mm Dive case with 300m water resistance, anti-reflective sapphire crystal, drilled lugs and a bi-directional ceramic bezel with 24 clicks. The watch has the Seiko NH34 onboard and comes with our new vulcanised Tropic rubber strap. A new tapered oyster bracelet with a milled clasp will be available as an optional extra.