Janus is the ancient Roman god honored by January, the month named for him, at the New Year.
Janus was associated with beginnings, transitions, doorways, passages, and time. His name is the source of January, from the Latin Ianuarius. Because New Year's marks a transition from one year to the next, Janus became especially appropriate to Roman ideas about the opening of a new period.
Roman representations commonly show Janus with two faces, conventionally looking in opposite directions. This imagery is often interpreted as connecting the past and future, although Janus's wider religious role included entrances, exits, and changes of state. The two-faced image is not a statement that he was deceitful; that modern interpretation can distort his Roman significance.
January 1 eventually became the opening of the Roman consular year, though Roman calendars and political practice changed over time. The Julian calendar reforms of 46 BCE helped standardize the calendar used in the Roman world. Modern January traditions are not direct replicas of one ancient festival, but the month’s name preserves Janus's connection with beginnings.