What kind of weird holidays have you heard about? Or perhaps participated in?

Forget the big holidays we all know about, whether you celebrate them or not. All holidays have social factors that drive them, and for those who celebrate it, it’s most likely traditional.

However, I just learned that International Pillowfight Day exists. This seems to occur globally, although I can’t really find any specifics as to why, (one source said it was some Internet thing) and there’s never any significant dates that this really needs to respect. People just set it up, it’s really like a huge event rather than a holiday. if that made any sense So pillow day is in the name of fun. There was one in Montréal, and I didn’t even know…
I’d be tempted to go, really. Thousands of pillows everywhere…except the thing is, most of the pillows end up being destroyed and ruined, and that sucks. All those poor pillows, destroyed. I don’t like it.

There must be all sorts of weird holidays and traditional events that are weird as hell though. Some fascinating, some disturbing…maybe some are cruel. Heard of anything? Participated in any?

What are the holidays, what do they center around, and do you like the idea, or did you like it if you participated? Why or why not?