What is the name of the two-headed Roman god who gave his name to a month of the year?

The ancient Romans depicted this unique deity with two faces, one looking to the past and the other to the future. This powerful symbolism made him the god of all beginnings, endings, and transitions. It was therefore fitting that the first month of the year, a time for reflecting on what has passed and looking ahead to the new, was named in his honor. The month of Ianuarius, or January, is a direct tribute to him.

Beyond the calendar, he was the divine guardian of all doorways, gates, and archways—both literal and figurative. He presided over the first hour of every day and was the first god invoked in any prayer, even before Jupiter. A famous temple dedicated to him in Rome had its doors ceremonially opened in times of war and closed only during rare periods of complete peace, symbolizing the state's own passage between conflict and tranquility.

Unlike many Roman gods who were adapted from Greek mythology, this two-headed deity was a distinctly Roman creation, one of their oldest and most important. His influence even extends into modern English. The word "janitor," originally meaning a doorkeeper or porter, shares its root with the name of this ancient guardian of passages.