Janus is the Roman god who gives January its name and is symbolized by looking toward both the old and new year.
Roman tradition associated Janus with beginnings, transitions, gates, doorways, and passages. He was commonly depicted with two faces, one looking forward and one looking backward. That image later became a powerful New Year's symbol because the holiday marks a transition between the year that has ended and the year that is beginning.
January is named from the Latin Ianuarius, the month of Janus. The name does not mean that Janus was simply a god of New Year's Eve; his broader role concerned openings and change. Modern images of a two-faced “old year” and “new year” often draw on this ancient association, though they are modern cultural adaptations rather than standard Roman holiday characters.