The Greek Old One, Cthulhu wishes all of you Hronia Pola!
Oxi Day is a Greek holiday celebrating when the Greeks told Mussolini to stick it in his ear. It was quickly followed by the Italian army invading Greece, which was quickly followed by the Italian army failing to capture Greece, which was quickly followed by Hitler and his boys coming to their rescue.
It is a very Cthulhuloid sort of holiday, an ancient alphabet, impending doom, denial, bloody resistance, mountains of death, Nazis, screaming death from the skies, muha ha ha ha!
BTW I can't use Greek characters, but it is pronounced like Oh-khee, not ox-ee (the second letter is a khee, not ksee).