What is the origin of another April Fool's Day (Tianxiang Festival) in China?

Tianxiang Festival originated in the Song Dynasty and was related to Song Zhenzong.

Related allusions

The ancients believed that human beings and nature were interrelated, especially emperors and princes, and their luck directly affected all kinds of visions in the sky. Thus, the most ironic scene in history ―― Song Zhenzong's "The Book of Heaven" began, which is really a good show of self-deception.

Song Zhenzong was bewitched by the treacherous court official. By washing away the humiliation of the League of Nations, he drove away the good minister and accepted the treacherous court official. In order to create a false auspicious feeling, he even bribed the minister with money, deceiving himself first and then others, and then sang a fake play in a big way and directed farce after farce. Song Zhenzong is unprecedented. ?

In the first year of Ganxing, a genius who faked the master and fooled the people finally died in Yanqing Hall at the age of 55. Although a series of excellent plays directed by him declared the end of the play, and the important prop of the play, "The Book of Heaven", was buried in Yongding Mausoleum by courtiers according to his wishes, his superb means were still inherited by later rulers.