The standard time everywhere is Greenwich Mean Time plus (+) or minus (-) the time difference between hours and minutes in the time zone. Many countries also adopt daylight saving time (DST). For example, the United States implements DST from April to September every year, one hour in advance. Beijing is named "Beijing time" because it is located in the East Eighth District of the international time zone, which is 8 hours different from Greenwich Mean Time (UTC) (that is, Beijing time = UTC +8 hours).
Extended data:
All of China (Chinese mainland, Hong Kong, Macao and Taiwan provinces) use Beijing Time (UTC+8), but in Xinjiang and Tibet, although the demarcation points of government agencies, enterprises and institutions and postal communication fees are all expressed in Beijing Time, they are two hours later than other provinces. For example, China Telecom's long-distance telephone discount time was delayed for two hours in Xinjiang and Tibet.
The method of calculating a local time zone is to divide the local longitude by 15, and then round it to an integer, which is the number of local time zones. For example, east longitude 127 degrees is 8 according to the above method, so east longitude 127 degrees belongs to the East Eighth District; The east longitude 128 degrees, calculated according to the above method, is 9, so the east longitude 128 degrees belongs to the East Ninth District.
References:
Baidu Encyclopedia-Beijing Time