User blog comment:Aaronsclee/When is the Hogwarts acceptance letter posted?/@comment-26129158-20150220163730

The only reason that Harry got his on his birthday and not the week before is becuase his Aunt and Uncle kept it from him. I think that (and this is only my opinion) everyone gets their letter a week before their birthday or so. It says on Pottermore (which is the most accurate because it is moderated by Rowling herself) that Minerva Mcgonagall got hers in October on or near her birthday