If you need a refresher on Ferris Bueller's Day Off because basic cable has taken half the day off from showing it on constant loop, it's about a student named Ferris Bueller who takes a day off. Years later, fans were left wondering the same thing: "Where did Cameron's dad bury the body after he got home?" Other, less morbid fans just wanted to know exactly when Ferris' day off was.
That's where Baseball Prospectus writer Larry Granillo comes in: He noticed that the movie used real footage and play-by-play commentary in its depiction of the Cubs game that the kids take in while playing hookey. Because the movie was released in the summer of 1986, Granillo deduced that the game took place during the '85 season. After looking through the game logs, he dug up four games where the Cubs pitcher we see on-screen faced the Atlanta Braves in the friendly confines of Wrigley Field. From there it was just a matter of piecing together the other clues in the commentary to determine that Ferris' day off was on June 5, 1985. Granillo even figured out that the foul ball Ferris caught was hit by Atlanta right fielder Claudell Washington in the top of the 11th. That's right, the Claudell Washington.