The Roman god Janus gave his name to January, the month that begins the Gregorian calendar year.
Janus was associated with beginnings, transitions, doorways, passages, and endings. Roman artists often represented him with two faces, conventionally interpreted as looking in opposite directions. That imagery made him a natural symbolic figure for the turn from one year to the next: one face could be imagined as looking back, while the other looked forward.
The Latin name for January, Ianuarius, developed into the month name used in English and many other languages. January 1 became an important civic starting date in the Roman calendar tradition, although calendar systems and local New Year customs varied across history. Janus should not be confused with Saturn, whose festival Saturnalia influenced later winter-season traditions but did not provide January's name. The modern Gregorian calendar retains January as its first month.