Janus is the Roman god associated with looking backward and forward, and he gives January its name.
Janus was linked with beginnings, transitions, doorways, gates, and passages. Roman artistic representations commonly show him with two faces, one looking toward the past and one toward the future. This symbolism made him especially appropriate for the boundary between one year and the next.
The Roman month Ianuarius, named for Janus, became the source of the English word “January.” January 1 became the start of the Roman consular year in 153 BCE, although Roman calendars and year-start practices changed over time.
Janus is sometimes mistakenly described as the Roman equivalent of a Greek god with exactly the same role. He is distinctive within Roman religion and has no straightforward Greek counterpart. The word “January” survives even though modern New Year customs are not Roman religious ceremonies.