What does "Xu Na" mean in the Gregorian calendar? thank you

The origin of the yellow calendar:

In ancient times, it was calculated and published by Qin Tian Jian, so it was also called the imperial calendar. According to legend, the yellow calendar was created by the yellow emperor, so it is called the yellow calendar. It is also called the farmer's calendar because it guides farmers' farming opportunities. Folk commonly known as the general book. However, because the word "book" and "lose" in Tongshu are homophonic, it is also called "Tong Sheng" because of taboo. The solar calendar is based on the lunar calendar in China, and there are many calendars indicating the good or bad of a day. The main contents of the Gregorian calendar are the schedule of the 24 solar terms, the good and bad luck of each day, and the luck of the zodiac.

The origin of the yellow calendar:

According to legend, the Huangli calendar was created by Emperor Xuanyuan, so it is called the Huangli calendar, which is also commonly known as the "general book" among the people. However, because the word "book" and "lose" in Tongshu are homophonic, it is also called "Tong Sheng" because of taboo.

China had an almanac in the Qin Dynasty at the latest as a guide to people's lives. From about the Song Dynasty, the magic number of "avoiding evil spirits" appeared in the almanac. Taiding has a five-year period (1328), and there are more than three million official almanac books.