20 December is the 354th day of the year (355th in leap years). There are 11 days remaining until the end of the year.
- 1993: Harry Potter, Ronald Weasley, and Hermione Granger start working on Buckbeak's defence.
- 1995: End of the term at Hogwarts School; Hermione Granger arrives at 12 Grimmauld Place.
- 1996: Professor Horace Slughorn hosts a Christmas party in his office for his favourite students and other associates. Harry Potter discovers that Professor Severus Snape made an Unbreakable Vow concerning Draco Malfoy.
- 1997: Luna Lovegood is kidnapped by Death Eaters while on her ride back home on the Hogwarts Express.