User blog comment:Aaronsclee/When is the Hogwarts acceptance letter posted?/@comment-4002547-20120204141051

Many people I've talked to before believes it to be around the student's birthday. Personally I think that'd be borderline insane. Sure, it's special and all - but it would also be an administrative nightmare. To prepare and send out a bulk of letters is less time consuming than sending them off one by one over the year, especially since they'll need to schedule teachers to inform the muggleborn students.