It is related to "weather phenology". The introduction of astronomy in the book Huai Nan Zi in the Western Han Dynasty contains "On the fifteenth day after the vernal equinox, when you point to B, the wind will be clear"; The record of Qingming in Hundred Questions at the Age is that "everything grows clean and bright at this time, so it is called Qingming". Although there are some differences in the text descriptions in these two ancient books, they actually say a truth, that is, "everything presents a clean and clear phenomenon and feeling". Tomb-Sweeping Day is the fifth solar term in 24 solar terms. At this time, the sun has crossed the equator for two weeks (the spring equinox solar terms directly hit the equator), and the sunshine in the northern hemisphere is gradually lengthening, with long days and short nights. After beginning of spring, after three solar terms: rain, fright and vernal equinox, the cold deep in the earth in the winter is being pulled out from the surface by the warmth brought by the sun and dissipated. At this time, the spring flowers are brilliant, the thick green covers the earth, the sky is clear, the air is fresh, and everything is born in time and is full of competition. It can really be described as "the wind is clear and the gas is positive" and "thriving".

2. Understanding from a humanistic perspective. "Qing": the sky is light and clear, but it rises. The sky is clear but not turbid, transparent and bright; God is pure and selfless, and is blessed by all things. "Ming": being familiar with things, it is clear to follow the trend. The ancients used the word "Qingming" to declare that future generations should be honest and upright, do things clearly, and be "honest and clean".

Sacrificing ancestors during the Qingming Festival, communicating with ancestors, let ancestors judge whether the actions of strangers in the world are honest and clean. As the old saying goes, man is doing and the sky is watching. The sky contains ancestors. Ancestors only bless those descendants who are upright and do things clearly. Therefore, people who post notices should always be vigilant, work hard, and be alert at all times. The law has been strict.