"Who on earth wants to talk to you this badly?"
-- Dudley Dursley
It’s a Saturday morning. The milkman delivers two dozen eggs to Aunt Petunia by way of the kitchen window. To her consternation, she discovers a Hogwarts letter rolled up inside each of the eggs. She shreds them in her food processor.
According to the text, this is Saturday, and it's two days before Harry's birthday.