(1) The first day of the year is the first day of the first lunar month.

(2) The calendar newly promulgated by the emperor.

The so-called new moon is the first month, which is the first month of the year. The new moon means the first day, and a new day is the first day of every month.

Together, it is the first day of the year. So the original meaning of Zhengshuo is the first day of a calendar.

But before Emperor Wu of the Han Dynasty, the new moons of the dynasties were not unified.

Silver moon (January) is the first year of Xia Dynasty, and the first day of January is the first day of Xia Dynasty.

The ugly month (December) is the beginning of Shang Dynasty, and the first day of December is the first day of Shang Dynasty.

The first day of November is the first month of the Zhou Dynasty.

The first year of Qin Dynasty is the first month of October, and the first day of October is the first day of Qin Dynasty.