Events that occurred on 21 December.
On Earth
- 1927 – Father Christmas writes a letter to J.R.R. Tolkien's children.
- 1933 – Father Christmas writes a letter to J.R.R. Tolkien's children.
- 1933 – J.R.R. Tolkien writes a letter to R.W. Chambers.
- 1955 - J.R.R. Tolkien writes a letter to Mrs. Rachael Feichtmeir.
- 2001 – Tom Shippey published "Temptations for All Time", a review of The Lord of the Rings: The Fellowship of the Ring for The Times Literary Supplement.
In Arda
- T.A. 3018:
- The Fellowship of the Ring rests in Rivendell and prepare for their quest to destroy the One Ring.