The unified time used in China is Dongba District (that is, Beijing time), while the unified time used in France is Dongyi District (that is, Paris time), with a difference of seven time zones. If it is 5pm in France, the China time is 12pm.
Time zones are defined by using the same time for regions on the earth. 1884 When the International Longitude Conference was held in Washington, D.C., in order to overcome the time confusion, it was stipulated that the world was divided into 24 time zones.
In order to overcome the time confusion, an international longitude conference (also known as the International Meridian Conference) held in Washington in 1884 stipulated that the world should be divided into 24 time zones (East 12 time zone and West 12 time zone). Britain (the former site of Greenwich Observatory) is defined as the central time zone (zero time zone), East 1- 12 and West 1- 12. Each time zone spans longitude 15 degrees and the time is exactly 1 hour. The last east-west zone 12 spans longitude 7.5 degrees respectively, and is bounded by east-west longitude 180 degrees. The time on the central meridian of each time zone is the time uniformly adopted in this time zone, which is called time zone. The time difference between two adjacent time zones is 1 hour. For example, the time of China East Zone 8 is always 1 hour earlier than Thailand East Zone 7 and 1 hour later than Japanese East Zone 9. Therefore, people who travel abroad must adjust their watches at any time to keep up with local time. Set your watch back to 1 hour every time you go westbound (for example, from 2 o'clock to 1). Set your watch forward 1 hour every time you go east (for example, from 1 to 2 o'clock). It is also stipulated that Britain (the former site of Greenwich Observatory) is the prime meridian, that is, the zero meridian.