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brief introduction
The local time on the Greenwich meridian, or the time zone (intermediate time zone), is called Greenwich Mean Time (also translated as Greenwich Mean Time), also known as Universal Time. Greenwich mean noon was originally used as the beginning of the average solar day, but it is inconvenient to use. Therefore, in 1928, the International Astronomical Union decided to take the mean solar time from midnight GMT as universal time, which is also commonly known as Greenwich Mean Time. 199965438+On February 28th, a new time system-Greenwich Electronic Time (GET) was officially born, which will provide a time standard for global e-commerce. However, the original Greenwich Mean Time (GMT) will still be used as the world standard time of 2 1 century.
GMT is the abbreviation of Greenwich Mean Time, which is called Greenwich Mean Time in Chinese. It is the standard time in Britain and the reference standard of time all over the world. The standard time difference between China and Britain is 8 hours, that is, the local time in Britain is 8 hours later than Beijing time in China.
BST is the abbreviation of "British daylight saving time", that is, "British daylight saving time" is one hour faster than GMT, starting at the end of March and ending at the end of 10 every year. In daylight saving time, the time difference between China and Britain is 7 hours.
At the Washington International Longitude Conference held in 1884, although the methods of calculating local time in various countries were stipulated, in some major global events, a unified time that everyone in the world abides by is still needed. Therefore, the international standard time is stipulated. It requires that the time on the zero longitude line be used as the international standard time on a global scale. Because the zero longitude line passes through the Greenwich Observatory in Britain, the international standard time is also called Greenwich Mean Time, also called Universal Time.
International standard time is widely used. It was first used for navigation and positioning, and later it was also used for Antarctic scientific investigation. In Antarctica, the latitude is very high, the longitude is particularly concentrated and the time zone is very narrow. In addition, the sun is not obvious at noon, and time has little to do with people's work and rest activities at that time. Therefore, scientific research stations in Antarctica use international standard time. In addition, international standard time is also used in international agreements, international communications, astronomical observation and calculation, and some international affairs to achieve global consistency.
Theoretically, noon at Greenwich Mean Time refers to the time when the sun passes through the Greenwich Meridian (the highest point over Greenwich). Due to the uneven speed of the earth in its elliptical orbit, this time may be different from the actual solar time by 16 minutes.
Greenwich mean time is no longer used as standard time because the daily rotation of the earth is somewhat irregular and slowly slows down. The new standard time is Coordinated Universal Time (UTC), which is reported by the atomic clock.
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