But what does GMT actually mean and how did the GMT function come to be built into watches? What are the characteristics of a GMT watch? How do you set the second or third time zones on the different types of GMT watches and how do you read the times? All these questions will be answered in this article.
GMT time – meaning and history
GMT stands for Greenwich Mean Time. This refers to the time zone division that representatives from 25 nations agreed on in 1884 at the so-called International Meridian Conference in Washington as a reference for world time.
Until then, each country and sometimes even individual regions had their own time, which was based on the highest position of the sun and announced by the respective church towers or station clocks.
This worked quite well until technical progress, especially in the field of railroad traffic and telegraphy, led to the desire for a uniform time or uniform time zones.
The solution was to introduce a worldwide standard time to which everyone could orient themselves. At the International Meridian Conference in 1884, Greenwich Mean Time (GMT) was chosen. Twenty-four of the 25 country representatives there voted for Greenwich Mean Time as the official prime meridian. The fact that the Greenwich meridian was chosen also had to do with the fact that this meridian was already used in navigation.
In 1972, GMT time was replaced by the so-called Coordinated Universal Time (UTC) as the world time.
The GMT function on watches
Circula AquaSport GMT with 24-hour bezel
For the GMT function, the interaction of the GMT hand and GMT bezel is crucial. Therefore, these two components will first be examined in more detail.
GMT hand
The GMT hand is an additional hour hand that stands out visually from the rest of the hands due to its size and usually distinctive color, and can be moved dependently or independently, depending on the type of GMT watch. Unlike the normal hour hand, the GMT hand needs 24 hours to circle the watch face once.
GMT bezel
In addition to the GMT hand, the GMT bezel also plays an important role in watches with a GMT function. The GMT bezel can be used to set the second or third time zone. Like the GMT hand, the GMT bezel displays 24 hours and is usually two-tone to distinguish between day and night. Unlike the diving watch bezel, the GMT bezel can usually be turned in both directions.
Correct setting of a GMT watch
To set a GMT watch correctly, you first need to know what kind of GMT watch you actually have.
There are two different types of watches with GMT function:
- First generation GMT watches, where the hour and GMT hands can only be moved simultaneously.
- Second generation GMT watches, where the hour and GMT hands can be moved independently.
Second generation GMT watches can be further divided into Office-GMT or Caller-GMT and True-GMT or Traveller-GMT.
The Circula AquaSport GMT is an Office-GMT
Setting a first generation GMT watch
In the first generation GMT watches, the GMT hand and the hour hand cannot be moved independently of each other because they are connected. This means that whenever you move the hour hand, the GMT hand moves at the same time. It is important to understand that the hour hand moves in a 12-hour interval and the GMT hand moves in a 24-hour interval.
If you want to display a second time zone on a GMT watch of the first generation using the GMT function, you first set the hour hand to display the local time. For the second time zone, the 24-hour GMT bezel is then aligned with the accompanying GMT hand so that the hand points to the corresponding number on the bezel that displays the time of the desired time zone.
This means, for example, that if it’s 8 p.m. (winter time) in Germany, it’s 2 p.m. in New York. The GMT hand is at the 10 o’clock position on first generation GMT watches. To display New York time, the bezel is now turned until the GMT hand points to the 14 o’clock marker on the bezel.
Setting a second generation GMT watch
In contrast to the first generation, the GMT hand and the hour hand of the second generation GMT watches can be moved independently of each other.
As mentioned above, there are two different types:
- Office-GMT or Caller-GMT, where the GMT hand usually indicates a foreign time zone, and
- True-GMT or Traveller-GMT, where the GMT hand usually indicates the home time.
Setting a Caller-GMT or Office-GMT
On the Office-GMT, the GMT hand can be set forward by turning the crown in the second position and – if the watch has a date display – the date can be changed by turning the crown in the other direction. This does not change the local time, which is very convenient.
In the third position of the crown, all hands move together.
Circula AquaSport GMT with three time zones
So, to set a second time zone, only the GMT hand needs to be aligned with the bezel.
If you also want to set a third time zone, then you also align the GMT bezel with the GMT hand, just like on the first generation GMT watches. In this case, you have to orientate yourself for the second time zone on the hour indications on the dial and multiply this number by two, because the GMT hand needs 24 hours for one rounding of the dial and not only 12 like the normal hour hand. Some GMT watches, such as the Circula AquaSport GMT make it easier to read a 3rd time zone by adding an additional 24-hour indicator on the dial.
So, if you are sitting in Germany at 8pm (winter time) and you want to use an office GMT to display New York time and Beijing time, you first use the second crown position to set the GMT hand to 2pm (New York) and then you align the bezel so that the GMT hand points to 3 o’clock (Beijing).
Setting a True-GMT or Traveller-GMT
On the Traveller-GMT, turning the crown in the second position allows the hour hand to be set for local time in either direction, while the GMT hand does not move.
In the third position of the crown, all hands move together.
Thus, to set the new local time after arriving in another time zone, one only needs to set the hour hand for the local time, while the GMT hand, which indicates the home time, does not move. With an additional third time zone, one aligns the GMT bezel with the GMT hand accordingly, as with the other two GMT watch types.
So, if you landed in New York at 2 p.m., you use the second crown position to set the hour hand to 2 p.m., while the GMT hand stays at 8 p.m. (Germany). To additionally display the time in Beijing, you can also adjust the bezel of this GMT watch type so that the GMT hand points to 3 o’clock.
So, if you landed in New York at 2 p.m., you use the second crown position to set the hour hand to 2 p.m., while the GMT hand stays at 8 p.m. (Germany). To additionally display the time in Beijing, you can also adjust the bezel of this GMT watch type so that the GMT hand points to 3 o’clock.
Office-GMT vs. True-GMT
As the names of the two GMT watch types and also the descriptions already suggest, the Office-GMT is better suited if you want to display the time of another time zone with the GMT hand and the Traveller-GMT is better suited if you are traveling and want to keep an eye on your home time with the GMT hand.
The reasons for this are simple: If you have a Traveller GMT, although you are actually mainly in your home time zone, then every time you set the time, the GMT hand moves with it (3rd position of the crown). This means that you first have to set the watch so that the GMT hand is at the desired position, and only then can you set the hour hand accordingly.
It’s exactly the other way around with the office GMT when traveling: Since only the GMT hand can be moved separately here, when traveling you first have to adjust all hands (3rd position of the crown) to set the local time and then the GMT hand has to be set to the home time again (2nd position of the crown).
When traveling, the Traveller-GMT is therefore more practical, because with the 2nd crown position you can simply adjust the hour hand to set the local time while the GMT hand remains unchanged for the home time. In the office, it’s the other way around. Here, the Office-GMT is more suitable because the second crown position allows you to set the GMT hand separately while the local time does not change.
Circula AquaSport with GMT function
Circula AquaSport GMT is a classic Office-GMT. It is the perfect choice for those who spend most of their time in their own time zone and maintain contacts in other time zones.
Circula AquaSport GMT with Sellita SW330-2 in Top grade
In addition to the bezel, the GMT watch from Circula has an additional 24-hour scale on the dial, so reading the different times is possible at a glance even with a third time zone!
Instead of the Sellita SW200-1 movement, which is installed in the diving watch AquaSport II, the Circula AquaSport GMT uses the Sellita SW330-2 movement in top version. This special top-of-the-line GMT caliber is based on the ETA 2892-A2 and enables a second time zone display by means of a centrally located GMT hand.
Unlike the unidirectional rotating bezel of the AquaSport II diving watch, the sapphire crystal bezel of the AquaSport GMT can be rotated in both directions. The bezel features 48-clicks and the indexes are filled with Swiss Super-LumiNova® BGW9.
The other specifications of the Circula AquaSport GMT are the same as the Circula AquaSport II:
- Scratch-resistant, slightly domed and inside double anti-reflective sapphire crystal
- Hands and indexes filled with Swiss Super-LumiNova® C3 X1
- 200 meters water resistant, screw-down crown (lumed)
- 40 mm diameter, 46 mm lug to lug and 12.6 mm height
powered by Borlabs Cookie