One of the lesser-known deities today of the Roman pantheon was Janus. He was the god of endings and beginnings, of transition and change, of doorways and arches. I suppose a simpler way to put this would be to say he was the god of duality. To this end, he is depicted as having two faces – one on either side of his head. He looks forward and back at the same time.
He is also generally agreed to be the deity that the month January is named for. January, as the first month of the Gregorian calendar, is both an ending and a beginning, it is the month of transition and change, and it looks both forward and back.