Almanack And Booke Of Dayes
Mentioned in Lords and Ladies and Maskerade, this book is popular in outhouses throughout the Ramtops. As the days pass, you can tear them out of the Almanack and put them, uhh, behind you. It is often the only book people read regularly. (Well, once, anyway...). This could well be the same thing, in-universe, as The Celebrated Discworld Almanak.