May 11, 868 is the date of the oldest dated book. It is a copy of the Tang-dynasty Chinese version of the Diamond Sūtra discovered in 1900 in the Mogao Caves near Dunhuang in northwest China. The caves are the repository of thousands of ancient manuscripts.
The International Dunhuang Project (IDP) was formed in 1994. Much of its early work focused on conservation and cataloguing. But these have been supplemented in the past few years with digitization, education, and research. The IDP DATABASE offers high-quality images of the manuscripts and other material, with cataloguing and contextual information.
Interestingly, millennia before Creative Commons, the Chinese Diamond Sūtra had an explicit public domain dedication. Its colophon at the end claims it was created “for universal free distribution.”