The Two-Faced God: Janus
He is usually depicted as having two faces, since he looks to the future and to the past. It is conventionally thought that the month of January is named after Janus (‘Ianuarius’).
In ancient Roman religion and mythology, Janus (/ˈdʒeɪnəs/; Latin: IANVS (Iānus), pronounced [ˈjaː.nus]) is the god of beginnings, gates, transitions, time, duality, doorways, passages and endings.
While the fundamental nature of Janus’ functions is still debated, most modern scholars agree around the essence of his existential principal: Leading all beginnings and transitions, whether these are abstract or concrete, sacred or profane. Interpretations of Janus’ identity either limit his duties to this general function or emphasize a concrete or particular aspect of it (i.e. identifying him with the light of the sun, the moon, time, movement, the year, doorways, bridges etc.). Another view point treats him as some kind of cosmological phenomenon, describing him as a uranic entity.
Almost all of these modern explanations were originally formulated by ancient scholars.