What Is A GMT Watch?

 
Akram S. from Jeddah, Saudi Arabia asks:

What does the GMT feature on a watch do or show?

 

"GMT" stands for Greenwich Mean Time and is the "0" point on the 24 hour scale of international timezones. Greenwich is in England, and from there other timezones are plus (+) or minus (-) GMT. GMT was established so that travelers would be able to quickly to know what time it is all over the world as long as they knew what the GMT time was and what to add or subtract from that time to get the local time on another place.

GMT watches were developed mostly for aviation purposes and include both the "local" and "GMT" time. Though in reality GMT watches tend to be used in different ways than their original purpose of knowing the local time and GMT only. By the way, GMT is also know as "UTC" (especially in some German watches).

It is also worth noting that there are watches with a GMT label that are not true GMT watches. True GMT watches must offer at least one time on a 24 hour scale. There are some watches with two time zones each in a 12 hour format. These, while useful, are not true GMT watches.

Most GMT watches have two hands to display the time in a 12-hour format and an independently adjustable 24-hour hand. If the 24-hour hand is not independently adjustable, it merely serves to indicate whether the time is AM or PM. Though some people set the GMT time to their local time in order to use it for just that purpose - to know whether it is AM or PM.

Many people use GMT watches to know their local time, and some other time zone that is usually not GMT. Thus, GMT watches are typically used to know the time in any two time zones (not necessarily your local time and strictly GMT). In addition, many GMT watches have a rotating 24 hour bezel. Assuming there is a GMT scale on the dial as well, this rotating bezel can be used to track a third time zone (you just need to do a little math).

To recap, GMT watches are used to show two timezones at once, with traditionalists setting the GMT hand to the actual GMT time. You can then add or subtract to GMT to know the time pretty much anywhere in the world. Second to chronographs, GMT complications are probably the most useful features on a watch, apart from the time itself.

For a dynamically updated list of every GMT watch we cover, look here »


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2 comments
roger the goodgion
roger the goodgion

Question about terminology:

If you are say in a time zone that is GMT+2 and it is daylight savings time (DST) and that area observes it, do you refer to that as GMT+1 or GMT+2 in DST? just wondering what the accepted ways to express that are.

T_I
T_I

Just a small correction, UTC is not the same as GMT.

 The GMT timezone has daylight saving time, UTC doesn't. (So the statement is half correct, during winter time ;) )