What does it mean to count to nine? How to calculate?

In China, the lunar calendar uses "99" to calculate the season, and the winter solstice is the first day of "99", and every nine days is called "99", the first nine days are called "99", the last nine days are called "29", and so on.

Jiujiu, also known as Winter Jiujiu, is a folk solar term of the Han nationality. The number 9 starts at the end of the solstice in the early winter of the Gregorian calendar 65438+ every year. There is no exact information about when the custom of counting nine originated. However, it was popular at least in the Northern and Southern Dynasties. "Liang Chao Shu Jing Chu Chun Qiu" records: "The winter solstice is 998 1 day, which is the end of cold." Count nine cold days, that is, from the solstice of winter, count a "nine" every nine days until the "99" of 81 days, and the weather will warm up. In fact, it is "99-99, plowing cattle everywhere"-90 days, which is 9 days.

In the traditional culture of Han nationality, nine is the extreme number, which is the largest, largest and longest concept. Nine nines is eighty-one, which is the "maximum" number. Ancient Han people thought that September 8 1 day must be the spring after the winter solstice.