From very early in the Christian era, the Feast of the Annunciation has been celebrated on March 25, commemorating both the belief that the spring equinox was not only the day of God's act of Creation but also the beginning of Christ's redemption of that same Creation. The earliest source stating December 25 as the date of birth of Jesus was Hippolytus of Rome (170–236), writing very early in the 3rd century, based on the assumption that the conception of Jesus took place at the Spring equinox which he placed on March 25, and then added nine months. While the Roman cult of Sol had existed in Rome since the early Republic, it was on 25 December AD 274, the Roman emperor Aurelian made it an official cult alongside the traditional Roman cults.