Events that occurred on 12 January.
 On Earth
- 1917 - Tolkien's leave of absence (to recover from his trench fever) ends, but he is far from recovered.
- 1928 - A New Glossary of the Dialect of the Huddersfield District, containing a Foreword by J.R.R. Tolkien, is published.
- 1930 - Musician Glenn Yarbrough is born.
- 1941 - J.R.R. Tolkien writes Letter 42.
- 1959 - Simon Tolkien is born.
- 1966 - J.R.R. Tolkien writes a letter to David Hicks.
- 1992 - The "International Tolkien Symposium" is held in Aachen, Germany.
- 2009 - The Image of Man in C.S. Lewis is re-released.