The Roman god who presided over doors, beginnings, and the new year was Janus.
Janus was a distinctly Roman deity associated with gates, passages, transitions, beginnings, endings, and change. He is usually portrayed with two faces, one looking forward and the other backward, a visual symbol of movement between past and future. January, or Ianuarius, takes its name from him.
Romans invoked Janus at the start of religious ceremonies and important undertakings because beginnings were thought to influence what followed. January 1 was dedicated to him as the opening day of the year. People exchanged good wishes, offered cakes made from spelt and salt, and gave gifts called strenae, including coins and seasonal foods.
The Temple of Janus in the Roman Forum became famous for its doors. Tradition held that they stood open during wartime and closed during peace, turning the building into a public symbol of Rome’s military condition. Janus is sometimes confused with Portunus, who also governed doorways and harbors, but Janus had the broader authority over transitions and beginnings.