John Carter of Mars Shifts Release Date

According to Deadline Hollywood Disney has moved up the release date of John Carter of Mars from June 8, 2012 to March 9. Originally that date was occupied by the studio's Frankenweenie which has moved to October. You can read more at http://www.deadline.com/2011/01/disney-shifts-release-dates-on-john-carter-of-mars-and-frankenweenie/ This sudden change though makes me wonder. Why is Disney suddenly moving one of their big tentpoles into the wasteland month of March? Possibly the fact that Pixar had their big film Brave set for release a week later? And how about the fact that Fox has set Ridley Scott's sci-fi epic Prometheus for the same date? I wonder how long before one of them blinks and changes dates again.