Along with "It's a Wonderful Life," this delightful holiday fantasy is one of the top Christmas movies of all time. Ironically, the film, which won three Academy Awards, including one for supporting actor Edmund Gwenn, as the Macy's Santa Claus who insists he's the real deal, didn't open during the yuletide season. This "Miracle" arrived on May 2, 1947. It was 20th Century Fox head Darryl F. Zanuck who insisted it come out during the summer to attract bigger audiences. The studio's promos kept the fact that it was set during Christmas a secret.
Los Angeles Times