The “best” is dating events in Holy-Roman era books. Aside from the variable of several years, then there’s also that some sects date from “birth” others “baptism” or “death”.

Further, each time the book got hand copied, you’ve no idea whether that monk copied verbatim dates OR believed (possibly wrongly) that the prior copy was dating heretically, and took the liberty of “correcting” it.

So several iterations along, book could be stating a century off…

Isn’t that the Secret Squirrel that Harvey Birdman represented to defend “whipping out his gadget?”