That was old 1.0 lore - the 'Dusty Tomes' were items you could view in each class Guild Hall back in FFXIV 1.0, and gave those little tidbits of lore. However, as you've noted they have not returned in ARR, and some of the things they mention may possibly have since been retconned (the '8 day week thing' for instance might be a holdover from FFXI, which also has an official 8 day week in order to give each day a name of one of the 8 elements on the elemental wheel).

So yeah, take them with a grain of salt.