From the winter solstice to Sunday, the calendar is 8 1 day, and every 9 days is called "September 19", which is named "September 19", "February 29" and "September 99" in turn. It also refers to the last nine days of the Ninth Five-Year Plan. Xue Neng's poem "Han Temple Pray for Rain to Return to Yangchun Pavilion" in Tang Dynasty said: "The Ninth Five-Year Plan has started from the south, and the sand has begun to build new fences in the north." The south solstice is the winter solstice. Zhao Yi's poem "Eliminating Cold" in Qing Dynasty: "In a blink of an eye, the cold will be over ninety-nine, and the spring will be fine."