How did the Tang Dynasty associate painting heroes with the 24 solar terms?

In feudal times, one of the forms of the emperor's rewarding meritorious service was to draw the image of the hero in a special building and indicate his deeds. This move began in the Western Han Dynasty, especially in the Tang Dynasty. However, it is still rare to associate screen heroes with solar terms. In the seventeenth year of Zhenguan (643), Emperor Taizong painted twenty-four heroes in Lingyange. "Think of the hardships of that year and feel the wind and cloud of that year." There are more than 24 founding heroes. Why choose only 24 instead of 25 or 34? This is to add "just like twenty-four qi helps the sky" Twenty-four Qi is the seasonal change caused by the different positions of the earth around the sun, which goes round and round and never stops. The so-called twenty-four qi are: beginning of spring, rain, fright, vernal equinox, Qingming, Grain Rain, Changxia, Xiaoman, Mangzhong, Summer Solstice, Xiaoshu, beginning of autumn, Chushu, Bailu, Autumnal Equinox, Cold Dew, First Frost, beginning of winter, Light Snow, Winter Solstice, Slight Cold and Severe Cold. Painting twenty-four heroes will not be opposed to twenty-four qi respectively, but just a side meeting. Without twenty-four qi, it is not a day; Without the help of heroes, the emperor can't be an emperor. On the other hand, there is a certain regularity in the movement of the twenty-four qi around the sky, and it doesn't matter if there is no regularity; Heroes fight according to the will of the emperor; Without a unified will, there is no hero. It is based on this understanding that painters draw twenty-four heroes and attach twenty-four solar terms. The twenty-four heroes refer to Hejian Li, Li, Du Laigong Ruhui, Wei Zheng, eldest grandson Zhao Gongmowgli, Liu Li, Wei Gongjing, Li Yinggong Ji, Liu Kuigong Hong, eldest grandson Pi Gongshunde, Yu Yongxing Gong Shinan, Wei Chie Gong Jingde, Xiao Songgong Yu, Zhang Yonggong Jing and Qu Yong. The above 22 people were recorded in "Quan" Volume 629 "Lu Wenling Fu and Preface". According to the record of "Yan" in Volume 9 of History of Famous Paintings, in addition to the above 22 people, there are 24 people including Bao, Zhuang Gong, Chen Guogong and Hou. Emperor Taizong personally praised him and said, "I cherish the memory of heroes, thank you for your death, and carry forward the righteousness of sages, which will last forever."