Events that occurred on 12 October.
 On Earth
- 1944 - J.R.R. Tolkien writes Letter 84.
- 1944 – J.R.R. Tolkien sends Leaf by Niggle to the Dublin Review, which hosts a short-story competition. It was published in the January 1945 issue.
- 1955 - J.R.R. Tolkien writes Letter 172.
- 1966 - J.R.R. Tolkien writes a letter to Kenneth I. Rasmussen, Jr..
- 1972 - J.R.R. Tolkien writes a letter to Rayner Unwin.
- 1979 - The Jackanory episode "The Last Stage" is aired on the BBC.
- 2004 - The Lord of the Rings Symphony in Milwaukee, Wisconsin.
- 2007 - Ring*Con 2007 in Fulda, Germany.
 In Arda
- F.A. 495:
- T.A. 3018: