21 August is the 233th day of the year (234th in leap years). There are 132 days remaining until the end of the year.
- Arthur Weasley, along with his sons Ron, Fred and George Weasley, pick up Harry Potter from Number 4, Privet Drive in order to take him to the Quidditch World Cup the following day.
- (Unknown Year): Terry Boot's check-out of Quidditch Through the Ages from the Hogwarts Library ends.
Behind the scenes
- 1989: Robert Knox, who plays Marcus Belby in the film adaptation of Harry Potter and the Half-Blood Prince, is born.