Apr 13
One of the oldest stories of King Arthur is found in The Dream of Rhonabwy, in the Mabinogion. While Rhonabwy sleeps, he has a vision of Arthur playing chess against his follower, Owain, to the backdrop of the Battle of Badon.
Neither player wins, however, with Arthur throwing a temper tantrum and smashing the board before the game is complete! Rhonabwy eventually awakes, to find he has been sleeping solidly for three days.