Janus is the ancient Roman god whose name gave January its name and who is associated with New Year transitions.
Roman mythology presents Janus as a god of beginnings, endings, transitions, doorways, gates, and passages. He is commonly depicted with two faces, one looking forward and one looking backward, making him an enduring symbol for the movement from an old year into a new one.
The Roman month of January, Ianuarius in Latin, was named for Janus. The modern New Year's date of January 1 has roots in the Roman calendar and civic practice, although different cultures and historical periods have begun the year on other dates.
Janus is not the Roman equivalent of Saturn, whose festival Saturnalia took place in December, nor is he simply a god of celebrations. His importance comes from transition and thresholds. Modern New Year's references to looking back and looking ahead echo this symbolic association, even when no religious ritual is intended.