How to calculate the number nine in the northern solar terms song

Counting nine solar terms is the "Nine Nine" of the Song Dynasty. To be exact, it starts from "Winter" and counts backwards for nine days. The first nine days are called "Jiujiu" ... and the last nine days are called "Jiujiu", one ***8 1 day.

Every nine days, the weather will change differently. With long-term experience, the ancients let people know the trend of cold and warm changes intuitively and vividly through the phenomenon of late winter and early spring. On the ninth day, winter has passed and spring is coming.

In the traditional culture of China, nine is the extreme number, which is the largest, largest and longest concept. Nine nines is eighty-one, which is the "maximum" number. People in ancient China believed that after the solstice on September 8 1 day, spring must have arrived.

In the northern solar term Song 1929, no moves were made. In 3949, I walked on the ice, planted willows along the river in 5969, opened the river in 79, brought geese in 89, and plowed cattle everywhere. ?