31 August is the 243rd day of the year (244th in leap years). There are 122 days remaining until the end of the year.
- 1991: Harry Potter asks his Uncle Vernon for a ride to King's Cross Station in London the following day. He agrees only because he is already going to London to have Dudley's tail removed at a private hospital.
- 1992: Harry Potter and the Weasleys have dinner at the Burrow, at the end of which, a fireworks display is held.
- 1993: Harry Potter meets Ron Weasley and Hermione Granger at Diagon Alley. Hermione purchases her pet Crookshanks and Ron buys Rat tonic for Scabbers from the Magical Menagerie.
- 1995: While staying at 12 Grimmauld Place, Ron and Hermione receive notification that they have been appointed Gryffindor's new Prefects. Molly Weasley purchases a Cleansweep Eleven for Ron, and later confronts a Boggart. Sturgis Podmore stood guard beside the entrance of the Department of Mysteries and was subsequently put under the Imperius Curse by the Death Eater Lucius Malfoy. Eric Munch caught Sturgis Podmore trying to break into Department of Mysteries at one o'clock in the morning.
- 1996: Harry Potter comes to the conclusion that Draco Malfoy has joined the Death Eaters
- 2008: Lily Potter is born sometime prior to this date and sometime after 1 September, 2007 to Harry Potter and Ginny Weasley. Hugo Weasley is born sometime prior to this date and sometime after 1 September, 2007 to Ron Weasley and Hermione Granger.