Over at GetReligion we analyze how well the mainstream media write about religion news. (Answer: Not very well!) Over the course of my six years there, I've noticed a trend around Easter or other high holy days where media outlets release shocking news meant to undermine Christianity. The Christmas tradition is a bit different. That's where media types tell folks that Christmas is actually a Pagan holiday.
For instance, everyone knows that Dec. 25 was an arbitrary date stolen from Pagans celebrating Saturnalia, right?
You can read William Tighe's fuller treatment of the topic here, but I'll summarize for you.
Early Christians chose what is now Dec. 25 (calendars have changed a bit, obviously) as the likely date of Christ's birth based on a widely held belief of that era that great prophets were conceived and died on the same date. They called this "integral age." Early Christians calculated that Jesus died on what would work out to March 25 -- the date for Passover of the year of his death.
You add 9 months and what do you get?
My favorite part of this story? In all likelihood, Aurelian probably set his sun festival for the same date in an attempt to co-opt what was already becoming a minor Christian feast day. The actual Pagans of that era had their sun festivals in August.
No, my actual favorite part of the story is probably that these myths about how the date was chosen were started by Christians. One was a Protestant trying to undermine the liturgical calendar. The other was a Benedictine monk trying to show how you could co-opt the culture without it causing harm. If only they knew ...