Zone time: a system of time measured in a uniform global time zone. When the sun is shining, it is twelve o 'clock at noon. But the time when the sun shines is different in different places. For example, it is 12 noon in Shanghai, and it takes five hours for residents of Moscow to see the sun. It's already 2pm in Sydney, Australia. So if all places use the local time standard, it will bring a lot of inconvenience to the administration, transportation, and daily life. To overcome this difficulty, astronomers came up with a solution: divide the world's longitude by 15 degrees, so that there are 24 zones. The uniform time standard is adopted in each area, which is called "zone time". The difference between adjacent regions is one hour. When people go east from one area to an adjacent area, they set their clocks one hour ahead. Go a few hours faster if you walk through a few areas. In contrast, when people moved westward from one area to an adjacent area, they set their clocks back one hour. Set back a few hours if you walk through a few areas. At airports and other transportation centers. The corresponding districts of the world's major cities are often illustrated to facilitate travelers.