A while back I heard/read Lawrence Kelemen’s “real story of X-mas” which pretty much covered everything. One of the topics of discussion was Saturnalia. This hearkened back to a story I read way back in the Talmud (Maseches Avoda Zara) when regarding Kalenda. Here’s what it says:
The Mishna, the 2nd century codex of the Jewish Oral tradition, states: “These are the festivals of the idolaters: Kalenda [beginning the new Calendar, i.e., New Years], Saturnalia [beginning Dec. 17 and ending Dec. 25]… . (Talmud Babylonian, Tractate Avoda Zara 8a)
Our Rabbis taught: (ibid):
When Adam HaRishon saw the day getting gradually shorter, he said, “Woe is me, perhaps because I have transgressed [with the Tree of Knowledge], the world around me is being darkened and returned to its state of chaos and confusion (tohuand bohu); this then is the mode of death to which I have been sentenced from Heaven!’ So he began keeping an eight days’ fast. But as he observed the winter equinox [December 21] and noted the day getting increasingly longer he said, ‘This is the natural way of the world’, and he took it upon himself to keep an eight days’ yom tov(sacred festival). In the following year he appointed both (the eight days preceding and following the winter solstice – the shortest day of the year) as yomim tovim (plural). Now, he designated them for the sake of Heaven, but they [the idolaters] designated them for the sake of idolatry.
Rabbi Chanan ben Raba said: Kalenda is kept on the eight days following the [winter] solstice, Saturnalia on the eight days preceding the equinox. As a mnemonic aid use the verse, “You have formed me behind (back) and before (front)” (Psalms 139-5) (Note: The chronological order in the Mishnah is reversed. Kalenda actually follows behind Saturnalia and Saturnalia comes before Kalenda.)
This explains why, a holiday dedicated by one of the holiest people in history (Adam) is not celebrated by Jews. What was once a holy period became sullied with idol-worship. There you go.
I personally used to wonder why December 25th became the holiday of Saturnalia, then succeeded by Kalenda. One answer I heard (and this made sense to me) was that Dec. 22 was a little bit longer than Dec. 21, Dec. 23rd to Dec. 22, then Dec. 24th to Dec. 23rd. After 3 consecutive days there was a Chazaka (a safe assumption that something consistent was happening). That was the reason that the day afterward became a holiday.
So now you know why Dec. 25th has such significant pagan origins and why it became ripe pickings for the “birthday” of another person we know about.