What is it often said in geomantic omen to build large and small moons?

The lunar calendar can be divided into big and small months and leap months.

The so-called "moon building" of the ancients linked the twelve months of a year with the twelve days in the sky. Twelve Chen is a concept of ancient astronomy, that is, dividing the day around the ecliptic (that is, the route of the sun moving once a year in the sky) into twelve equal parts, with twelve branches from east to west: Zi, Ugly, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu and Hai. Twelve branches match December and are called "Building the Moon", "Building the Ugly Moon" and "Building silver moon". So how is December determined? This problem is related to the rotation of the Big Dipper. The Big Dipper is seven bright stars in Ursa Major, which are distributed in a bucket shape. Tian Xuan (Xuan), Tian Ji (Xuan) and Tianquan form a fighting body. Yuheng, Kaiyang and Yaoguang make up the bucket handle, which is called the watch in ancient times. Connect Tian Xuan and Shu Tian with a straight line, extend the distance to Doukou by about five times, and you will meet A star in Ursa minor, which is now Polaris. Polaris is a bright star that appears in the northern part of the sky. It is very close to the north pole of the earth, almost opposite to the earth's axis. From the point of view of the earth, its position has hardly changed. Sailors and travelers often rely on it to tell their directions. Because the Big Dipper revolves around the North Star, the second Big Dipper is also used to tell the direction and set the season. We can decide the season according to the direction pointed by the Big Dipper in bucket handle at the beginning of Twilight: bucket handle points to the east, and the world is spring; Guide to barrel handle, it's summer in the world; Bucket handle refers to the west, and the world is autumn; The barrel handle refers to the north, and it is winter all over the world. Similarly, we can determine December according to the different positions in the twelve days indicated by the Big Dipper in bucket handle. Bucket handle refers to the son of twelve branches, which is the sword month, that is, the first month of the weekly calendar; Bucket handle refers to the ugliness among the twelve branches, which is the ugly month, that is, the first month of the lunar calendar; Bucket handle refers to the twelve Yin, which is silver moon, that is, the first month of the summer calendar, that is, the "three positive" mentioned in the last blog post. By analogy, bucket handle refers to one of the twelve branches, that is, building the moon, which is called "building the moon". The structure of the moon is very important to judge this matter.