The Internet exists for exactly this reason: In a four-year old post for Baseball Prospectus, Larry Granillo looked closely to determine exactly what Cubs game Ferris Bueller and his friends attended in the 1986 classic Ferris Bueller’s Day Off.

And based on what little information about the game we get from the movie — mostly the scene where Ed Rooney watches a portion of the broadcast inside a pizza place — Granillo determined that the game that provided the setting happened on June 5, 1985, exactly 30 years ago Friday. This is the 30th anniversary of Ferris Bueller’s day off.

The gory details:

The movie “Ferris Bueller’s Day Off” was released on June 11, 1986. The ballgame then must have been filmed either real early in the 1986 season or sometime during 1985. Looking at game logs from those seasons, we see that there was no game in 1986 in which Lee Smith (#46) faced the Braves at Wrigley Field. There were four such games in ’85, though Smith left the Braves hitless in one of those. Of the remaining three games, it isn’t hard to find the game we’re looking for. Ferris Bueller and his pals were at the June 5, 1985, tilt between the Cubs and the Braves. The foul ball that Ferris caught was hit by Atlanta rightfielder Claudell Washington (#15) in the top of the 11th inning. The game was tied at two (not scoreless, like the pizza guy claimed) and backup second-baseman Paul Zuvella (#18) was being held on first by Leon Durham (#10) after a leadoff single (the fourth hit of the game, and Atlanta’s first hit since the fifth). Washington would end his at-bat with a flyball to leftfielder Davey Lopes. The next batter, Rafael Ramirez, would wind up hitting a two-run home run and the Braves would go on to win 4-2. The movie, however, cut away before that happened.

As Granillo points out, the length of the game would have made it awful tough for Ferris to visit the art museum and go swimming and still get home by 5:55, but then it’s only a movie. And after Granillo’s original post, an assistant director on the production wrote him to say they actually filmed at a Cubs-Expos game in late September.

But obviously the June 5 date should stand as the day on which the movie is set, if only because it makes a lot more sense for high-school seniors to be cutting school and facing an uncertain future in June than in September.