'A Festivus miracle': What to know about the 'Seinfeld' holiday celebrated on December 23
As a card sent to him by his father reminded George in the 1997 episode, Festivus comes every Dec. 23. In real life, it was invented by the father of former “Seinfeld” writer Dan O’Keefe in 1966. O'Keefe incorporated it into the show when he wrote "The Strike" episode.