Deliberate mistake: In the scene inside General Kohler's command center when Kohler is giving Colonel Hessler a tour of the war room he points out to Hessler a clock on the wall whose increments represent 1 hour and that the attack has to be over within so many hours. Later in the movie, just when the attack starts, this dormant clock's hand immediately springs forward and ticks through 2 increments, thus representing 2 hours passing in 2 seconds.