First of all, Chongqing is located in the northern hemisphere, in the southwest of China. This means that the sunset time is 18:00 local time and the sunrise time is 06:00 local time. This is a natural phenomenon caused by the rotation of the earth.
Secondly, Chongqing's geographical location is close to the equator, which means that the days are long in summer, so it gets dark later. In winter, the days are shorter, and it gets dark earlier.
Therefore, because of the geographical location and seasonal influence, it doesn't get dark until 8 pm in Chongqing. This is the law of nature and the beauty of nature.