It's a day-by-day calendar of the events of the book. I expect you to be roughly accomodating. For example, some time in the last week Sirius Black has escaped from Azkaban, and Remus Lupin has been offered the job as Defense professor at Hogwarts. If this is the sort of thing about which your characters might care, it'd be dandy to react or something.
That is all.
Ooh, P.S. I know the game does not technically start until September first, but posts before that are highly encouraged because they make Kirby happy. You want to make Kirby happy, don't you? Oh, you know you do.
P.P.S. Possibly, I'll keep a running tab of canon events on the main community board, if someone asks me really, really nicely. Just, y'know, to make it easier.