According to this, it was Satan himself. https://m.youtube.com/watch?v=JgUQVupc_VU
We have 10 fingers. You count to 10 then start over. Then caesar egos inserted 2 months. So now count to 12 and start over.
I figure it's because back then we had a superior base-12 (60?) numbering system.
Yeah, seems like the "holiday season" is actually all based upon the days beginning to get longer in the northern hemisphere (the rebirth of the sun, so to speak: also see Alban Arthan)
Edit: further info --A video came to my attention today that points out Julius Caesar, who upon becoming empire of Rome, changed the times and the calendar to establish January as the beginning of the year, honoring the Roman god Janus. I'm going to post a new comment.
It was a mistake, April 1 makes much more sense. The Gregorian calendar caused January 1 to be new year. The Romans calendar was off, but they knew it, and had floating holidays to fix the calendar in which they partied and relaxed. The catholics didn't like the days off for no reason and strived to "fix" the calendar.
Pope Gregory XIII https://en.m.wikipedia.org/wiki/Gregorian_calendar
(post is archived)