The earth is divided into 24 time zones, 12 in the east and 12 in the west. With Greenwich Observatory in London as the zero time zone, the east 1 zone to the east 12 zone is in the east, and the west 1 zone to the west 12 zone is in the west. The eastern district is earlier than the western district. Longitude is a time zone every 15 degrees. For example, Beijing is located on the meridian of east longitude 120 degrees, belonging to the East Eighth District.
That is, the required time zone = divided by 15 degrees (the remainder is rounded to 4).