Beginning of spring is the first solar term, and the first earthly branch is Zi, but why is it not Zi Yue that surprises beginning of spring?

Suppose I made a calendar in ancient times. If the solar terms and the dry calendar are the products of the same period, then the first solar term must be the summer solstice or the winter solstice. In fact, China's dry calendar starts from the winter solstice, corresponding to 165438+ October (there are also ancient countries on the earth that took the summer solstice as the first "solar term", that is, ancient Egypt, and of course they also set one ...).

The reason is, of course, that we first determined that the "year" goes round and round, and the most remarkable feature is the change of the length of day and night. In a year, the winter solstice has the longest night and the shortest day, while the summer solstice is the easiest coordinate to find at the beginning of the year.

Like the summer solstice in the east, the spring and autumn equinox (not beginning of spring! ! ), that is, when day and night are equally divided.

When did beginning of spring and the 24 solar terms come into being? That was at least after China began to enter the agricultural society and the calendar needed help to guide the farming season. This is why beginning of spring is the beginning of the solar term. When did the twenty-four solar terms begin to be popularized throughout the country? Hanwu time!

The twenty-four solar terms are not based on the length of day and night, but on the seven stars in Ursa Major, commonly known as the Big Dipper, whose handle points (its spoon head points to the North Pole). From about 900 BC to 1000 years later, several stars in Ursa minor will take turns to be Polaris. However, because Polaris II, commonly known as the Emperor Star, is particularly bright around (second only to the current Polaris Gou Chen Yi), in fact, around 3000 BC, when Polaris still belonged to the constellation Draco in theory, people had directly regarded Polaris II as the Polaris and used it to find the first grade. )