The ever helpful Wiki:
thence also of gates, doors, passages, endings and time.
He is usually depicted as having two faces, since he looks to the future and to the past.
The Romans named the month of January (Ianuarius) in his honor.
Janus presided over the beginning and ending of conflict, and hence war and peace.
The doors of his temple were open in time of war, and closed to mark the peace.
As a god of transitions, he had functions pertaining to birth and to journeys and exchange, and in his association with Portunus, a similar harbor and gateway god, he was concerned with travelling, trading and shipping.
“you and your L pills. They go together well. There’s a stench of death about you. How to die like a hero. When the only important thing is how to live like a man.”