Janus, the ancient Roman god of beginnings and transitions, gave January its name and was honored during the year's transition.
Janus was commonly depicted with two faces, one looking forward and one looking backward. This imagery reflected his association with doorways, passages, beginnings, endings, and changes from one state to another. The Latin name for January is Ianuarius, derived from his name.
Roman religious practice included festivals and observances connected with Janus, especially at the start of the year. January 1 became the beginning of the Roman consular year in 153 BCE, when newly elected consuls began their terms on that date. The modern New Year's holiday is not simply an unchanged Roman festival, but the surviving name preserves a clear link to Roman ideas about beginnings.