Why do you say, "On August 15th, Yun Zheyue, it snows and lights on the 15th day of the first month"?

First of all, we should make it clear that the dates in the proverb "August 15th, Yun Zheyue, the 15th day of the first month" are all lunar calendar dates. The two calendar forms used by China, the fifteenth day of each month in the lunar calendar, happen to be the night of the full moon.

August 15th of the lunar calendar is the traditional Mid-Autumn Festival in China. On this day, people have the habit of appreciating Yue Bai. The 15th day of the first lunar month is the traditional Lantern Festival in China. On this day, we have the habit of eating Yuanxiao, putting on lanterns and enjoying lanterns.

Through long-term observation of the weather, the ancients accumulated life experience and practical experience and summed up some laws between solar terms, which are called "solar terms relationship". In other words, after a certain weather appears, the corresponding weather will appear in the next few days.

It is generally believed that this rhythm time is 30 days, 60 days, 90 days, etc. However, the difference between August 15 and August 1 month 15 is just 150 days, so this rhythm relationship holds. If there is a "Yun Zheyue" on August 15, then the "Snow Lantern" usually comes on the 15th of the first month.