Six qi and Yijing

Twelve hexagrams in the Book of Changes divide a year into twelve months, six of which belong to Yin and six to Yang. Judging from the two hexagrams of Gankun, there are five days to stay, three days to stay, and two days to rest. So there are 24 solar terms in a year, and different climate changes affect our life activities, resulting in the phenomenon of birth, aging, illness and death.

The classic of traditional Chinese medicine, Neijing, also has the same content. Su Wen's theory of six hidden images: "Five days is waiting, three days are waiting for qi, six qi is time, and four hours is age." Qi refers to the solar terms, one solar term is 15 days, six qi is a six-day solar term, and ***90 days, that is, three months, is a season.