Janus

In Roman mythology, the god of all openings, including doorways and passageways, and the beginning of the day, month, and year. January was dedicated to him. He is represented as having two faces, one looking forwards and one back, (in sculpture, a herm), and was associated with wisdom because he knew the past and could foresee the future. In Roman ritual he was invoked first in a list of gods, and at the beginning of any enterprise.

At the Forum, the doors of Janus (reputedly built by Numa Pompilius, king of Rome) remained open in war and were closed during peace.

His chief priest was the Rex sacrorum (the king as religious head of the state) but every head of a household was regarded as his flamen (sacrificial priest) . One of the oldest Italian deities, his name may have derived from janua ‘a gate’, or it may be the masculine form of Diana (Jana).