December date” of Christmas (Catholic Encyclopedia (1908)) or not has been called into question by Cardinal Joseph Ratzinger, now Pope Benedict XVI, who challenged this theory by arguing that a December 25 date was determined simply by calculating nine months beyond March 25, regarded as the day of Jesus conception (the Feast of the Annunciation).
Just as Christmas coincides with the winter solstice, the March 25 date neatly coincides with the vernal equinox, and its pagan ritual themes of fertility and sexual congress with nature that were later associated with Christianity and Jesus. Other recent Christian commentators agree with Ratzinger that the identification of Christ’s birthday pre-dates the Sol Invictus festival, noting the earliest record of the celebration of Christ’s birthday on December 25 dates to 243 AD.[citation needed] The question of the historical origin of Christmas, and its relationship to the festival of Dies Natalis Solis Invicti remains unresolved (it should be noted that the Romans also celebrated the end of the year with a festival called the Saturnalia, which ended on December 23).
Some Christians accept the idea that Sol Invictus may be behind the date of Christmas, with the idea that the early church “baptized” the holiday by imbuing it with a new, Christian meaning. In the 5th c., Pope Leo I (the Great) spoke of this in several sermons on the Feast of the Nativity. Here is an excerpt from his 26th sermon:
But this Nativity which is to be adored in heaven and on earth is suggested to us by no day more than this when, with the early light still shedding its rays on nature, there is borne in upon our senses the brightness of this wondrous mystery.
But this sermon was not in any way related to Sol