The lunar calendar is divided into big and small months and leap months.
The so-called "month construction" of the ancients is to connect the twelve months of the year with the twelve stars in the sky. Twelve chen is a concept in ancient astronomy, which is to divide a week near the ecliptic (that is, the route that the sun moves once in the sky once a year) into twelve equal parts, and assign them from east to west with Zi, Chou, Yin, Mao and Chen. , Si, Wu, Wei, Shen, You, Xu, Hai twelve branches. The twelve branches match the twelve months, which are called Jianzi month, Jianchou month, Jianyin month, etc. in order. This is called "month Jian". So how is December determined? This question is related to the rotation of the Big Dipper. The Big Dipper is a group of seven bright stars in the constellation Ursa Major, distributed in a bucket shape. Tianshu, Tianxuan (xuanyinxuan), Tianji (jiyinji), and Tianquan form the fighting body. Yuheng, Kaiyang, three shining stars form the handle of the bucket, which in ancient times was called dipper (biao Yinbiao). Use a straight line to connect the two stars Tianxuan and Tianshu and extend the distance about five times toward the Doukou direction to encounter the Ursa Minor A star, which is now the North Star. Polaris is a bright star that appears in the northern part of the sky. It is very close to the Earth's North Pole and almost directly opposite the Earth's axis. Its position is almost unchanged when viewed from the Earth. People who sail and travel often rely on it to identify directions. Because the Big Dipper rotates around the North Star, the Big Dipper is also used to identify directions and determine seasons. We can determine the season based on the direction in which the handle of the Big Dipper points at dusk: when the handle points to the east, it is spring everywhere; when the handle points to the west, it is summer; when it points to the west, it is autumn; when it points to the north, it is winter. . Similarly, we can determine the month of December based on the different positions in the twelve celestial bodies pointed to by the handle of the Big Dipper. The Zi among the twelve branches pointed to by the bucket handle is the month of Jianzi, which is the first month of the Zhou calendar; the Chou month pointed by the twelve branches of the bucket handle is the month of Jianchou, which is the first month of the Yin calendar; the Yin among the twelve branches pointed to by the bucket handle is Jianyin month is the first month of the lunar calendar. This is the "three positives" mentioned in the previous blog post. By analogy, whichever branch of the twelve branches the bucket handle points to is the month of that branch, which is called "moon construction". The moon construction is very important for judging the horoscope.