A watches bezel can have a multiple uses with the most common one being timing. As the bezel have five minute increments you can track up to sixty minutes just with the bezel and minute hand. It is very simple to do. Just line up the 60 minute mark of the bezel, it will usually have a triangle or arrow to make it easier to spot, with the minute hand and you’re done. As the minute hand moves around it will point to how many minutes have elapsed. This was originally designed as a way for scuba divers to track how much oxygen was left in their tank but nowadays is seldom used for that purpose.
There are other bezel features with the next most popular layout being the GMT layout. For a full guide on how to use a GMT watch you can read all about them here, https://theclassicwatchbuyersclub.com/blogs/blog-updates/gmt-watches. In the simplest terms you have an extra hand on a GMT watch that goes around in twenty four hours. So from 12 to 12 for an hour hand is twelve hours but for a GMT hand it is twenty four hours. This means you can set it to another time zone and track it against the bezel. Simply set your local hands to say UK time and your GMT hand to Washington hand. Then to read your GMT just look to see where the hand is pointing on the twenty four hour bezel. So for the Rolex pictured the local time is six and as the GMT hand is pointing to 18 the second time zone is six pm.
As you can imagine these functions came from necessity rather than style. As mentioned the dive time bezel was to, as the name suggests, time dives and the GMT was made for pilots. It was an elegant solution to the issue of time zones. The pilot would set their watch to local time and then leave the GMT hand on GMT time. Sometimes referred to as Zulu Time, but basically it is time zone 0. This served two purposes, one was a lot of these pilots were flying in and out of the UK so having a time zone pre-set to their destination was helpful. The second was with GMT being 0 time, if you know how much to add or subtract you can easily work out any other time zone. If you know that Paris is one hour ahead and your GMT hand says it is one pm then you know it is two pm in Paris. Similarly if you know New York is five hours behind and it is one pm in London then it is eight am in New York. So the GMT can be seen as both a second time zone tracker and if set to GMT time then time 0 from which you can quickly work out any other time zone.
Those are the main two bezels you will encounter but if you have any other questions please get in touch in the comments or email us at firstname.lastname@example.org