What is the main content of the ancient book Summer?

The oldest almanac in China is Xia Dynasty's Xia, which records people's knowledge of determining agricultural time by observing astronomical phenomena and phenology. It was originally collected by Dade, a ritual musician at the end of the Western Han Dynasty, and later circulated in a separate book.

According to research, Xia's words are only over 400 words. As far as astronomical knowledge is concerned, it records the monthly astrology in the order of 12 months, such as the stars that appear in the south in the morning and evening, the handle direction of Beidou, the position of the Milky Way in the sky, and where the sun reaches among the stars.

In addition, Xia also explained the monthly meteorology, phenology, farming and political activities. For example, in the first month, when you start to sting, you will see it when you lower your head. At first, you will faint in ginseng, and the barrel handle will hang down. Here "Ju" and "Shen" are both star names, and "bucket handle" is the spoon-shaped handle of the Big Dipper. According to the astronomical phenomena reflected in the book "Summer", it shows that China does have information of earlier times.