Why do you want to print books on Qixi?
Every year, Tanabata is a dog day, with high temperature and humidity, and books are easy to get wet. Scholars choose to take books to the open field to dry at noon on Tanabata to prevent damage.
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According to historical records, this custom originated in the late Eastern Han Dynasty nearly two thousand years ago. Mao Cui's "Four-person Moon Order" in the Eastern Han Dynasty said: "On July 7, I exposed my prayer clothes and I didn't smoke." This shows that there was a custom of uncovering books in Wei and Jin Dynasties.
During the Tang and Song Dynasties, printing books on July 7th was still very common. According to the Jihua Calendar of Tang, Han and Hubei, there is a custom of "hanging clothes in a flash" on July 7th. According to the book market records of the Song Dynasty, the ceremony of the Song Dynasty took July 7th as the book market. On that day, there were less than six departments in the three provinces, and each of them gave money to hold a banquet for the book fair.
There is an idiom called "Long Hao printed books". It is said that in the Western Jin Dynasty, Long Hao joined the army under Fu Huan Wen, who was knowledgeable and versatile. On July 7, when he saw others printing books, he unbuttoned his shirt and lay naked in the sun to dry his stomach. When asked, he said "I print books" to show his erudition, that is, to bask in his stomach.
Baidu Encyclopedia-Tanabata