Events that occurred on 31 December.
 On Earth
- 1925 – J.R.R. Tolkien's employment at the University of Leeds officially ends.
- 1943 - Actor Victor Raider-Wexler is born.
- 1960 - J.R.R. Tolkien writes letter 226.
- 1964 - J.R.R. Tolkien writes a letter to Ingeborg Korff and her pupils.
 In Arda
- Note: Months of the Shire Calendar only have 30 days, so no events have nor will happen on the 31st.