And there are enough canonized saints that every day has several of them (typically 5-10 each day, in the Book of Saints that my mom has, and I suspect that that’s an incomplete listing).
It used to be a lot more common to refer to days by whoever was the most prominent saint with that day as a feast, even if that saint wasn’t very prominent overall. Who here would have ever heard of St. Crispin, were it not for Shakespeare writing about a grand speech given before a battle on his day?
St. Swithun’s Day is my personal favorite.
That is unofficially April 20th.
A great book to pick up and browse through to see what people are commemorating on any particular day. I still have my copy from 2000. I see the current edition sells for around $30 more–I guess because of all the extra “days” they’ve added in the last 20 years? 
Kippers fan?
As that is also Adolph Hitler’s birthday it’s always seemed to me to be an inapt choice for Stoners’ Day.
Then again if the Nazis had had a lot more MJ they might have been a lot less beastly. Might.
That is why I have thought the exact opposite. Let Hitler’s birthday be taken over by a peaceful (some might say hippie) celebration. I also disengage my pedantry gene around that guy.
As for the OP’s question: I remember reading (or perhaps hearing on a podcast) about a day that someone just created and sent to the local news. It was a slow enough news day, and local news loves to have its more upbeat pieces, so it caught on in a few, and then spread. I don’t think they registered it anywhere until later.
I wish I could remember which “day” it was.
Good suggestions both.
Maybe we should make it a festival designed to especially annoy modern day Nazis. Something about celebrating ethnic diversity maybe.
Today is National Megalodon Day!