What is "number nine"? Write the content and meaning of number nine songs.

Jiujiu, also known as Winter Jiujiu, is a folk solar term in China. Counting nine starts from the end of December and the early winter of the Gregorian calendar to the date of Renren every year. It was written in the Records of the Age of Jingchu, a priest of the Liang Dynasty: "The number of winter solstice days and 9981 days are the end of cold." Counting nine cold days means counting nine every nine days from the date of the winter solstice, and counting until the eighty-first day of the ninth, the weather will be warm.

The content of "Counting Nine Songs": Don't shoot on September 19th and 29th; Walk on the ice in March 9 and April 9; 59 and 69, watching willows by the river; Seven or nine rivers open and eight or nine geese come; 99 plus 19, plowing cattle everywhere.

The meaning of "Counting Nine Songs" is to vividly record the changes of climate and phenology between the winter solstice and the vernal equinox, and express some laws of farming activities. "99" is a more applicable solar term in northern China, especially in the middle and lower reaches of the Yellow River.