International Meridian Conference
At the International Meridian Conference in Washington in 1884, the Greenwich Meridian, which was already in common use, was finally chosen as the internationally binding Prime Meridian. Greenwich Mean Time, or GMT for short, was then introduced so that one time standard could be relied on in different locations.
GMT and UTC
For watches with two time zones, this has been the customary term ever since and also forms part of the model name, as is the case with the different versions of the Rolex GMT Master II, the Panerai Luminor GMT models or the Hublot King Power Unico GMT.
In 1972, as a result of the extremely accurate measurements of time achieved using atomic clocks, the Universal Time Coordinated (UTC), or the Coordinated Universal Time, was introduced as a new time standard. Both terms, GMT and UTC alike, are employed synonymously in everyday usage.
Local time and the reference time
Air travellers have appreciated watches with the GMT function since the 1950s so they always know what the exact local time and the reference time in the second time zone are. Local time is displayed in the centre using the hour and minute hands. The reference time can be read using an additional hand in the centre or a smaller sub-dial. The local time remains unchanged if the reference time is adjusted for the second time zone.
Panerai Luminor GMT Automatic Accioaio
You can see this second time zone on the Tudor Black Bay GMT, for example, by using the 24-hour graduated bezel.
Tudor Black Bay GMT
A second central hours hand
In the case of the Breitling Navitimer 1 Chronograph GMT 46 models, a second central hours hand gives the reference time, and the display at 9 o’clock indicates whether this is a.m. or p.m. in the second time zone.
Breitling Navitimer 1 Chronograph GMT 46
Juwelier Wagner offers a wide choice of GMT models too thanks to the large number of brands in its range.