Events that occurred on 13 September.
 On Earth
- 1951 - Final day of the Congrès Internationale de Philologie Moderne at the University of Liège, a conference in which J.R.R. Tolkien delivers the paper "Middle English 'Losenger'".
- 1951 - Actor Bruce Phillips is born.
- 1974 - The first Oxonmoot is held at The Welsh Poney, Oxford.
- 1992 - The second part of the 1992 radio series of The Adventures of Tom Bombadil is aired on BBC Radio 5.
- 2002 - Oxonmoot 2002 at St Antony's College.
- 2014 - Oxonmoot 2014 at Lady Margaret Hall.
- 2015 - Oxonmoot 2015 at St Antony's College.
- 2019 - Oxonmoot 2019 at St Antony's College.
 In Arda
- T.A. 3018:
- T.A. 3019: