In the Song Dynasty, the first half of the 24 solar terms is 621, and the second half is 823. What does that mean?

The whole sentence "June 2 1 day in the first half of the year, August 23 in the second half of the year" means that there are two solar terms in each month in the first half of the year, the first solar term is around the 6th and the second solar term is around 2 1 day. In the second half of the year, there are two festivals every month, the first one is around the 8th, and the second one is around the 23rd.

Twenty-four solar term song is a poem compiled for the convenience of remembering the twenty-four solar terms in the ancient calendar of China. Solar terms refer to the 24 solar terms and climate. It is a calendar made in ancient China to express seasonal changes and guide farming. It is the crystallization of the long-term experience and wisdom of the ancient working people in China.

The ballad is as follows:

The spring rain shakes the spring and clears the valley, and the summer is full of mountains and summers.

Autumn dew, autumn frost, little snow in winter and cold in winter.

The two festivals remain unchanged every month, with a maximum difference of one or two days.

The first half of the year is June 2 1 day, and the second half is August 23.