This episode takes place in 1985, but Ghostbusters (1984) was released in theaters on June 8, 1984. While it's not specified what month this episode takes place, the June 8th release makes it impossible for that movie to still be in theaters by 1985.
The episode takes place in 1985. Both Chris and Greg skip school to see the movie Ghostbusters. The movie was released in 1984, a year before the episode takes place.