Janus is the Roman god whose name means “door” and who is linked with New Year beginnings.
Janus was associated with doors, gates, passages, transitions, beginnings, and endings. Roman artistic representations commonly showed him with two faces, allowing him to look toward the past and the future. That symbolism made him especially appropriate for the start of a new year.
The month of January, Latin Ianuarius, was named for Janus. In the Roman calendar reform associated with Julius Caesar, January 1 became the opening of the civil year in 45 BCE, although local and religious calendars did not always follow the same practice immediately.
Janus is often mistaken for a god of time in the modern sense. His principal role was transition and thresholds, not the abstract measurement of time. The familiar New Year connection comes from that transitional symbolism and from January’s calendar position.