EXCLUSIVE: FX’s hot new drama series American Horror Story‘s 13-episode first season will be actually 12.5 episodes. The horror drama’s first season finale on Dec. 21, which had been slated as two-hour, will now be 90-minutes. The trimming of the finale is a result of American Horror Story’s very aggressive production schedule which left no breathing room. The project was picked up to pilot in late February. Creators Ryan Murphy and Brad Falchuk couldn’t work on the pilot until they wrapped the second season of Glee, so it didn’t start shooting until late May. In a quick turnaround, FX picked up the pilot to series on July 18, and it was rushed to production 2 weeks later to make the Oct. 5 premiere date. With the first episode after the pilot doing some reshoots and some of the episodes requiring 8-day shoots vs. the standard 7 because of complex scenes, production on the series is now at a point where Episode 13 would wrap on Dec. 15, leaving no time for post-production to make the Dec. 21 air date. And because of the holidays, it didn’t make sense to push that last episode to Dec. 28 or the new year. Murphy had been discussing the issue with FX president John Landgraf for the past few weeks. There was an option for the series to drop the 13th episode altogether and air an hourlong finale, but I hear Murphy was able to put together a plan for a 90-minute episode to give viewers a satisfying ending. American Horror Story has already been renewed for a second season after a red-hot ratings run, punctuated by another series high this week, and I hear that its second season may be extended beyond 13 episodes.