What's the difference between the ancient lunar calendar in China and the present lunar calendar?

In ancient China, the lunar calendar was basically based on the period of the first lunar month, with leap months to make the average calendar year a tropical year, and 24 solar terms to reflect the seasonal changes. Therefore, different periods and dynasties had to revise the calendar to make it more accurate.

1 The ancient calendar of China before the Han Dynasty took 366 days as a year, and the "leap month" was used to determine the end of the four seasons and the year. There are already time units of day, month, ten-day and hour, and the technology of yin-yang calendar is available; The motion laws of the five planets and the sun and the moon were observed, and the time difference was adjusted by "leap moon" and "subtraction". The implementation of the calendar has become a major event, and one of the main contents is to determine the four-hour age by leap month and the positive leap surplus, that is, to determine the position of leap month and how to subtract the extra days (without missing days), so as to determine the end and start of the age.

At the beginning of Han Dynasty, there was a great turning point in China's calendar, and the national unified calendar became a relatively independent science and technology. Emperor Wu of the Han Dynasty instructed Li Han (taichu calendar), which was written in seven years.

Since then, the calendars promulgated by China in past dynasties have been similar to those of the Han Dynasty (taichu calendar). This shows that the calendar rules we use now basically follow the Han calendar (taichu calendar) of the Han Dynasty, which is quite different from the summer calendar before the Han Dynasty.