"Summer 99" starts from the summer solstice, and every nine days is a nine. There are nine nines and eighty-one days every year. Similarly, March 9 and April 9 are the hottest seasons of the year. In stark contrast to the ninth day of September in winter. Unfortunately, it has not been widely spread. In fact, Summer 99 does vividly reflect the relationship between date and phenology.
"99" in "99 sunny day" does not mean "99 Double Ninth Festival". In the traditional culture of China, nine is an extreme number, which means maximum and maximum. People in ancient China believed that spring would come after the 998th1day of the winter solstice. The "99" in the "99 sunny day" is the eighty-first day after the winter solstice, which is the early spring.
In ancient times, the working people in the north had relatively simple conditions to keep out the cold, and at the same time, because it was almost impossible to do farm work in winter, the common people generally regarded winter as "surviving" the past. In order to pass the time in the long winter, the working people invented this method of "counting nine", dividing the long winter into nine stages, making up proverbs and enjoying themselves. The custom of "counting nine" has also been passed down to this day.