Though relatively few people actually observe them as holidays. For most of us, they’re astronomical dates on the calendar, and get about a moment’s notice, at most.
Acadiana Day. In Louisiana, it’s the day after Thanksgiving. Weird coincidence.
We celebrated national Cheeseburger Day this year. Not sure if we’ll do it next year.
I also found out that that national Martini Day is June 19, which happens to be Mr. Middon’s birthday. Since I was going to have a martini anyway I don’t think you can say I really celebrated it though.
I am pretty big on Cinco De Mayo, Guy Fawkes Night (I am American) and Groundhog Day. None of those are exactly obscure but it isn’t like stores have display cases full of merchandise for them or that most people celebrate them.
I seriously wish half christmas from Workaholics was a real holiday. But I’d feel weird celebrating June 25th by myself.
Also not so much a holiday, but I’ve done calculations for my age and tried to celebrate certain round number landmarks.
10,000 days alive. Weeks alive that end in -000 (2,000 weeks alive comes up in a while). I’m not sure why people only celebrate annual birthdays. The average person lives about 30,000 days, which is about 4,000 weeks or 1,000 months. There are some landmarks in those numbers.
Let’s not forget National Gorilla Suit Day (January 31) when we put on our goriLla suits and distribute bananas to the deserving.
This was due to Mad magazine’s Don Martin creating a series of cartoons celebrating such a day. After his death, somehow it got accepted to the point of it getting a Wikipedia page, but later his widow asked that the whole thing be forgotten.
I celebrate U Day by wearing a brown coat and searching for an Alliance friendly bar. The fans seem to be settling on 9/20 as U Day, so it’s the day after Talk Like a Pirate day.
I also celebrate Jackie Cochran’s birthday in May. I find it interesting that one of the world’s first female test pilots died of old age. Typically, test and race pilots from the 1940’s exited in a more spectacular fashion. If I understand the records, at the time of her death she held more speed, distance, and altitude records than any pilot on earth, male or female, living or dead.
Similar to this, I celebrate my birthday. It has only occurred on .0000012% of the days that earth has been around - now that’s obscure!
I always remind everyone whenever Kesha’s birthday (March 1) or Dan Rather’s birthday (Halloween) is coming around. On Kesha’s birthday, I don’t listen to any non-Kesha music.
I did celebrate my billionsecondiversary.
No love for prehistoric creatures day? Or is that not obscure enough round here? 
It’s next week, remember!
My birthday is the only day that someone will do it for me. 
So, you sit in silence all day? 
Around here, Halloween is Nevada Day.
How appropriate that this thread should be started during the Jewish holiday of Sukkot, my wife’s favorite holiday. It is probably known to most Jews, but is celebrated by a relatively small percentage of them in the U.S., and I daresay is unknown to the vast majority of non-Jews.
I sure hope you took account of those pesky leap seconds they’ve been inserting.
Here in Chicago, we do Pączki Day for Shrove Tuesday/Fat Tuesday (it is also celebrated in other cities with a Polish-American population). Actually, the more hard-core Poles will also do Fat Thursday a few days previous (in Poland, Fat Thursday is celebrated.) But, hey, two excuses to pig out on pączki! (Jelly-filled donuts, bismarks, whatever you want to call 'em. They’re made from a rich sweetened dough with milk, egg, and butter–kind of like a brioche dough, but deep fried like a donut–and traditionally filled with plum or rosehip jam, but many varieties exist).
The International Mathematical Union is trying to create a “Mathematics Day”. Naturally for pi-day, 3-14. I will definitely celebrate it since it also just happens to be my anniversary and my wife and I always celebrate that.
PI days is one we do most years.
Hobbit Day is the other one. September 22nd. This is the shared birthday of Bilbo & Frodo Baggins.
We do small observances of the quarter and cross-quarter days. We also wassail our apple tree in January.
Talk Like a Pirate Day falls on my eldest child’s birthday, so we combine the two for extra celebratory fun.
I celebrate the birthday of the US Marine Corps, November tenth. I also celebrate myown birthday, which is also November tenth.
I hang a Marine Corps flag in front of my house, and if I ever get around to designing and having made my own personnal flag, I will display both on November tenth.