When was Bailuyuan?

The subject asked, "When is the Millennium?" The Millennium of 2023 is September 8.

According to the perpetual calendar, the Millennium of 2023 is September 8. Millennium is the 15 solar term in the "twenty-four solar terms", and the third solar term in autumn is the end of the application of the moon in the lunar calendar and the beginning of the unitary month. The sun reaches longitude 165 degrees, and the festival will be held on September 7-9 of the Gregorian calendar. It is an important solar term reflecting the cold growth of nature. As the weather turns cold, it is sunny and hot during the day, but the temperature drops quickly after evening, and the temperature difference between day and night is large.