Twelve detailed explanations

In ancient China, in order to observe the position and movement of the sun, the moon and the five stars, the zodiac was divided into twelve sections from west to east, called twelve o'clock. The names of twelve o'clock are: Jixing, Xu Anbi, Zhanglou, Daliang, Shishen, Quail Head, Quail Fire, Quail Tail, Shouxing, Fire and Shimu. These names have been recorded in Zuozhuan and Guoyu in the Spring and Autumn Period and the Warring States Period, which are used to describe the location of Muxing. In ancient times, the constant week of Jupiter was defined as twelve years, so it is generally believed that twelve times originated from the observation of Jupiter. It can be traced back to the Spring and Autumn Period or earlier. However, in Mandarin, Lingzhou dove (the astrologer of Wang Shi) said: "The king of Wu cut Yin and was older than the quail fire." According to China astronomer Yuzhe Zhang's research on the orbit of Halley's comet in recent years, it is believed that the attack time of King Wu should be 1057 BC. At that time, the old star was indeed in the second quail fire, so this statement of Lingzhou dove should be the actual observation at the beginning of the week. If this conclusion is reliable, then it is also possible to push the founding era of the Twelve Dynasties to the end of Yin and the beginning of Zhou Dynasty.

Qian Baoyu, a Chinese historian of science, believes that the division of twelve times was originally based on twenty-eight houses and four palaces (that is, four elephants), with three times in each palace. Because the width of the right ascension across the four palaces is uneven, the width of the twelve right ascension is also uneven. But later it developed into a system of equal division according to equatorial degrees. Hanshu Law has twelve starting and ending degrees, corresponding to twenty-four solar terms. Take the twelve solar terms as the starting point of each time and the twelve middle qi as the midpoint of each time. This division principle has been used until later. However, due to the influence of precession, the starting and ending degrees are gradually changing. After the end of the Ming Dynasty, twelve names were used to translate the zodiac, such as Capricorn Palace as Jixing Palace. However, the starting point of each palace was changed to correspond to the twelve meridians, and each palace was equally divided according to the longitude of the ecliptic. For example, the Jixing Palace at the starting point corresponds to the winter solstice, and so on.