Time zone division: each time zone spans 15 longitude. Draw a time zone with longitude 0 of 7.5 from east to west. The longitude range of instant zone 0 is 7.5° W-7.5 E, starting from 7.5 E and 7.5 W, and dividing a time zone every15 longitude in the east and west respectively, until the east 1 1 zone and the west1. The easternmost longitude of the east 1 1 region is 172.5 E, and the east 12 region is between 172.5 E and 180. The longitude of the westernmost part of the west 1 1 region is 172.5 W, and the west 12 region is between 172.5 W and 180. The east and west time zones 12 occupy longitude 7.5 respectively, forming a complete time zone, that is, the world is divided into 24 time zones. 12 has the same hours in the east and west, and the date difference is 1 day, so 180 is called the theoretical international international date line.

? Due to the rotation of the earth, different regions have different local time. In order to solve the problem of time confusion, the method of dividing time zones is adopted. The local time where the central meridian of each time zone is located is the time used in this time zone, which is called time zone. In fact, countries do not set time completely according to the time zone. Many countries set a legal time as their unified use time. For example, China local time 120 E is called Beijing time.