ante diem iii idus januarias
- Carmentalia begins (day 1) — a two-day festival (with a three day break between the days) in honour of the deity Carmenta, who was possibly a goddess of both childbirth and prophecy.
- 49 B.C. — Julius Caesar crosses the Rubicon (by another reckoning)
- ?? B.C. — dedication of the Temple of Juturna in the Campus Martius
- 29 B.C. — Octavian closes the doors of the Temple of Janus, signifying the Roman world was at peace