Explain "GMT watch"! It's very convenient. Do you know that usage? (LEON.JP)-Yahoo! Journalism

If you are interested in watches, you may have heard the name "GMT watches". There are 24 numbers written on the bezel, or a lot of city names written on the dial, which is the watch. Break the common sense of watches!? Black sports watches now look great and difficult to use, but GMT is a very convenient function for people who work and relate to people around the world. Let me introduce its functions and changes.

When did the concept of jet lag come into being?

A massive map of the world's time zone. If you add the time difference in the present place, you can know the present time in the parts of the world.

There is night and day in a day, but not the whole earth is day, or all is night. The earth revolves around the sun for a year and rotates at a speed once in 24 hours, so the place where the sun shines is day, and the place that misses is night. And the time of the place where people live needs to be defined according to the day and night cycle of that place. Occasionally someone will say, "it would be convenient to unify the time of the world," which is impossible. When the sun comes out, if it is at night and vice versa, it will be very difficult. Therefore, people in the world live at different times. However, in order to communicate with people in the world and make the business proceed smoothly, the moment of the world must be defined according to certain rules. In other words, if the rules of "it's time for Tokyo and time for London" are clear, you will know the time of other countries immediately and it will be easy to get in touch with them. So what comes into being is the concept of jet lag.

The time difference was determined at the International Meridian Conference in 1884. The earth rotates 360 degrees (360 / 24015) in 24 hours. The time difference is defined as one hour per 15 degrees longitude, and the world time is divided into 24 time periods (time zones). The birth of the concept of world time. The time determined as the origin of world time is the time of the Greenwich Observatory in London (Greenwich mean time = Greewich Mean Time=GMT). The time of 24 time zones in the world is defined as "a few hours from GMT".

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