Historical records and almanac can be divided into "Xia Zheng", "Andrew" and "Zhou Zheng", which is the popular "Three Meanings Theory" in the Warring States, Qin and Han Dynasties. Correction refers to which month the first month of a year in the lunar calendar starts. The monthly building refers to the month marked by twelve branches. From the south of the solstice (that is, the winter solstice), the bucket handle of Beidou refers to the moon, so it is the moon. After the second month, the order is ugly month, silver moon, ..., and before the second month, the reverse order is the sea moon, the moon, ... Therefore, the first year of Xia Dynasty is silver moon, the first year of Shang Dynasty is ugly month, and the first year of Zhou Dynasty is Zi Yue. The Qin dynasty believed that there were three orthodoxy, and it was a fact that Xia, Shang and Zhou orthodoxy alternated. However, it was extended and 10 was taken as the beginning of the year. Yuan Feng, the Emperor of the Han Dynasty, changed to taichu calendar in seven years, and one year ended with Yin Jianyue. Since then, Xia Zheng has been widely used for more than two thousand years. The usage based on the lunar calendar is as follows: when the first month of the lunar calendar is placed in the shade, the subsequent months are arranged in turn, February corresponds to Mao, March corresponds to Chen, and so on.

Generally speaking, the so-called monthly construction refers to twelve branches, such as Jian Zi, Jian Chou and Yin Jian. Some people think that the monthly construction refers to the size of the lunar month, so there is a fallacy that there is a big construction and a small construction. This is because the first day of the first lunar month has been adopted since ancient times, that is, the first day of the first lunar month. The traditional almanac records the monthly buildings in the column of month name, such as November 21 and Jianbingzi. When these labels are changed to "November construction, C" by mistake, there will be fallacies. The picture below shows the physical photos of Shen Da Datong calendar in the third year of Daming Jiajing, as shown.