The Occult! Yes it's a day to celebrate the occult arts such as palmreading and the Ouija Board.
The Ouija board was invented in 1890 and somehow made a transition from "harmless parlor game" to "divining tool" around the time of World War 1. That's probably because we stopped calling the living room the parlor about that time. Scientific studies have not shown that the Ouija Board is a way to communicate with spirits. But there are many famous cases of it's use including the following from Wikipedia:
Former Italian Prime Minister Romano Prodi claimed under oath that, in a séance held in 1978 with other professors at the University of Bologna, the "ghost" of Giorgio La Pira spelled the name of the street where Aldo Moro was being held by the Red Brigades in a Ouija. According to Peter Popham of The Independent: "Everybody here has long believed that Prodi's ouija board tale was no more than an ill-advised and bizarre way to conceal the identity of his true source, probably a person from Bologna's seething far-left underground whom he was pledged to protect."
Poets and songwriters have been known to use the Ouija board for inspiration or even to write lyrics for them. One woman claimed she channeled Mark Twain through the board to write an entire novel. That's a lot of Ouija board time!
But the most important use of the board is as a way to scare the pants off your friend in 7th grade at a slumber party to predict she would marry the pimply ugly creepy guy sitting by her in Social Studies class.
The Ouija Board is said to work based on a principle called ideomotor effect. This is what happens when you unconscious desires guide the movement of your muscles. Like when you find yourself at the refrigerator taking out the ice cream instead of getting on the treadmill.