Is there a time difference in cities in China?

Of course there is! According to the setting sun on the horizon, it is obvious that the coastal cities in southern China are dark at 8 pm, while the sun has not set in Qinghai and Gansu in western China. The time difference is at least 3 hours! But in China, Beijing time is used uniformly, not according to the setting time of the sun on the horizon! ! ! ! ! ! ! America is based on the time when the sun sets on the horizon! ! ! China's ancestors used the sun to calculate time! ! ! You got it? I think the answer is good. Give me a compliment! Thank you!