system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the purpose of the turnable dial around the face of a watch?
gpt
The ring as we know it today on some watches, also called rotating bezel, actually dates to the first diving watches of the 1950's. At the time, using a stopwatch was impossible, because every additional pusher could further compromise water-resistance, so instead they relied upon the bezel as a basic timing apparatus.

Right before a dive, the wearer aligns the zero mark on the minutes hand. The bezel then indicates the minutes passed since entering water. To add security, the bezel can only be turned counter clockwise, meaning that if it were accidentally rotated, the immersion time would appear longer and the diver would be compelled to return to the surface earlier.

During the 1960's and 1970's, the US and British Ministries of Defence also incorporated the bezel into military standard, either to display dive time or hours.