Janus

Janus, a very ancient Italian deity who presided over the beginning of the several divisions of time, as well as the beginning of all enterprises, in connection with which he was worshipped; he had two heads, or faces, one of which looked behind into the past and the other before into the future, and this power of penetrating into both it is said Saturn endowed him with as a reward for receiving him on earth when he was driven out of heaven.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)