When Christmas was Against the Law explains all the dates primitive Christians originally celebrated Jesus’ birthday, and why Saturnalia (pagan holiday) and Solstice influenced the final choice.
Christianity Today lists the possible dates for Jesus birthday as: “May 20, April 18, April 19, May 28, January 2, November 17, November 20, March 12 and March 25 — and … December 25 probably didn’t emerge as the favored date until late in the third century.”
CNN goes on to say, “That, intentionally or not, grafted the new Christmas onto the old Saturnalia, the most popular celebration of Roman times. The seven-day festival that started December 17 to honor the god Saturn and welcome the winter solstice gave us today’s tradition of holiday greenery, gift giving and the office party (or variations thereof), for the Saturnalia was a time of much drinking, some carousing, certainly unrestrained revelry.”
It’s interesting that the Jewish Sabbath, the 7th day, was also named for the god Saturn (still is). Saturn was kindofa fierce mean father-god, wasn’t he? He got turned into Father Time and we used to draw him as the “Old Year” every new Year’s Eve, and the baby he’s often depicted with was called the Baby New Year. (There’s a dark side to that story, that he “devours” the baby, and we also see Saturn depicted by ancient artists with baby cupid on his lap, cutting off his wings).
The Greeks and Romans originally thought the Jews worshipped Saturn since they revered the 7th day, Saturn’s day.