Or Birthday of the Unconquered Sun.
Sol Invictus - Wikipedia, the free encyclopedia
Sol Invictus was an official Roman Sun god. Like all their ancestors before them, and since humans had the intelligence to look up to the sky and notice stuff like the movements of the sun, the Romans revered the sun in proper pagan style and witnessed its annual rebirth and resurrection with a big party. Lots of booze, presumably.
At least this incorporeal, mythical jesus character was based on something real.
Happy Dies Natalis Solis Invicti. Have a good one.