Someone has made this explanation, in which "Jia Zi", "Jia Xu", "Shen Jia", "Wu Jia", "Chen Jia" and "Jia Yin" have a vertical line called "Liu Jia". This is a concept of time. What is emphasized above is the idea of changing from five to six. In Oracle bone inscriptions, the vertical lines of the first five columns have equinoxes, but the sixth column "Jiayin" does not contain equinoxes, so Hanshu says that "there are six columns in the day and five sons in the morning", which is in line with the trend of "May 6th". Change brings metaplasia. It was said in ancient times that the Emperor of Heaven should follow this principle, so Liu Jia represents an evolutionary trend.