What do you mean by eight stanzas?

"Eight festivals" refer to beginning of spring, vernal equinox, long summer, summer solstice, beginning of autumn, autumnal equinox, beginning of winter and winter solstice.

In the folk, there is often a saying that the four seasons are "spring, summer, autumn and winter". There are two versions of the "eight festivals", one is the eight festivals in natural solar terms, and the other is the sacrificial solar terms in folk customs, with different meanings.

As early as Shang Dynasty, there were four solar terms, namely, midsummer, midsummer, midsummer and midsummer. In the Zhou Dynasty, there were eight solar terms. At present, the earliest recorded document is China's oldest astronomical and mathematical work "Weekly Shu Jing", which reads: "Everything has eight sections and twenty-four qi." .

The date of the book "Zhou Li He suan Jing" is still controversial, and it should be no later than the Han Dynasty. This paper records the dialogue between Zhou Gongdan and mathematician Shang Gao in the early years of Western Zhou Dynasty, in which the most famous Pythagorean Law was put forward, which was much earlier than Euclid's geometric theory, the "father of geometry" in ancient Greece.

During the Three Kingdoms period, when Zhao Shuang, a native of Wu Dong, commented on Zhou Pian Shu Jing, his evaluation of "Eight Sections" was as follows: "Second, it was extremely cold and hot; Dichotomy, the sum of yin and yang; Four stands, the beginning of growth and collection; This is eight stanzas. " The second solstice is the summer solstice and the winter solstice, the equinox is the vernal equinox and the autumnal equinox, and Li Si is beginning of spring, Changchun, beginning of autumn and beginning of winter. Therefore, the eight natural solar terms are beginning of spring, Spring Equinox, Long Summer, Summer Solstice, beginning of autumn, Autumn Equinox, beginning of winter and Winter Solstice.