Festivus, a tradition for some since 1997. Steinfeld. A festival for the rest of us. Festivus pole, beer cans and duct tape. No deterioration. Speak your grievances, and feats of strength. Oh well.
Most cultures celebrate the end of this year or the beginning of the next about this time of the year. A festival of lights at the dark time of year or something. Saturnalia or old Rome, to celebrate the end of harvest and clean up the eat early portion of harvest. It was a slow agriculture work time for a bit, so why not have a celebration. Now we do it to excess perhaps.
Further north the natives burned big logs on the longest night of the year, and likely for a while to keep warm and provide a bit of light. The fierce Quadi decorated trees; with what, I have no idea, to mark their territory. Yule was born. Along come the Christians and add there concepts to the annual seasonal solstice or cultural/religious celebration, and take gifting to new extremes of excess, and we have the present situation. Oh well, in the end we all just die anyway.
The Celts celebrated eight time a year, the solstices and equinox and midpoints. Their greatest fear was the sky falling, aka meteorites, as they had experienced. They were a prolific culture, expanding from their root area to all of northern Europe and beyond. Add to their holidays a few christian holidays, and we have the current situation. Reminds of the Life of Pi, where Pi tries to follow three religions. A lot of holidays. Oh well.
In the Northern Hemisphere it is the cold part of the year, so heat, fire and lights would naturally be a big part of any celebration, as would be food and drink, much drink likely. Story telling is the original art, and that would feature in any celebration. Repeating the stories of old, a history lesson of sorts, modified by each story teller down through the ages, to improve, or as remembered or as created. The Stoics suggest we periodically go back to the behavior of that time for a few days, just to accustom ourselves to being without. Such an exercise willingly will remind us of the past and "prevent us getting to soft" as was one of their concerns. (like Epictetus frags 13) ( or Marcus Aurelius somewhere) Oh well, a bit of soul carrying around a dead body.