Janus is the ancient Roman god whose name gives January its name and whose symbolism suits New Year's reflection.
Roman tradition associated Janus with doors, gates, beginnings, transitions, and passages. He was often depicted with two faces, one looking toward the past and the other toward the future. That imagery made him a natural symbolic figure for the change from one year to the next.
The month January is named for Janus. The Latin name Ianuarius developed into the month names used in many modern languages, including English January. Roman religious practice honored Janus at beginnings and boundary moments, not only at the modern New Year's celebration.
The two-faced image does not mean Janus was simply a god of deception. In its original context, the faces represented his ability to oversee opposite directions and transitions. January 1 became the start of the Roman consular year in 153 BCE, helping strengthen the month's connection with official beginnings.