God Of Sunday - Devdutt Pattanaik In Roman times, Sunday was the first day of the week — an important day named after the Sun-God. Helios or Hyperion was the Greco-Roman Sun-God, who later merged with another Greek god, Apollo, the youthful, energetic, beautiful god who shot arrows that got rid of the darkness. When the Roman Empire became Christian, the day of the Sun became Dominica, the Day of the Lord, the day when — according to Christians — God rested after creating the world in six days.