The academy and CBS didn't realize that the 13th put the Emmys in conflict with the MTV Video Music Awards, which were scheduled for that same night.
Said Jack Sussman, CBS' executive vice president of specials, music and live events, "After we announced plans for Sept. 13, MTV informed us they were locked into the same day for the Video Music Awards, with venue and sponsorship agreements in place. We had the flexibility to move; they didn't. It's best for the industry and the audience that these events not compete against each other." [Variety]