Why are some solar terms after beginning of winter and some before beginning of winter?

There are 24 solar terms in China, which can accurately reflect the change of natural rhythm. It is the product of ancient farming civilization and represents the superb wisdom of our ancestors. In the international meteorological world, the twenty-four solar terms are called "the fifth invention", and there is a saying of "99" in the China lunar calendar, which is used to calculate the seasons. The calculation method is from the solstice of winter (counting from the solstice of winter, which means the beginning of cold), every nine days are called a nine, the first nine days are called a nine, the second nine days are called a 29, and so on until the ninth nine days, when the number reaches 998 1 day. At this time, winter has passed and spring has arrived.