according to cinematical, the film version of 'harry potter and the order of the phoenix' has been given an official release date of 13 july 2007, six days after the official release date of 07 july 2007 for the final book in the series. the good folks at cinematical feel that the proximity of release might be a bad thing which might end up causing either the publishers or the studio to balk and push back the release of one to avoid coinciding with the other.

http://www.cinematical.com/2006/04/07/potters-phoenix-gets-a-release-date/