Janus is the ancient Roman god who gave January its name and is symbolized by two faces.
Roman tradition connected Janus with beginnings, transitions, doorways, gates, and passages. His two faces were commonly interpreted as looking in opposite directions, making him an especially fitting figure for the threshold between the old year and the new one. The Latin name for January, Ianuarius, comes from his name.
The Roman calendar originally had a different structure, but January eventually became the first month in the Julian calendar introduced by Julius Caesar in 46 BCE. The calendar reform helped align the civil year more closely with the solar year and established January 1 as the start of the Roman administrative year.
Janus is often called a “two-faced” god, but that phrase can misleadingly suggest hypocrisy in modern English. In Roman symbolism, the two faces primarily represented looking backward and forward, not deceit.