The date of Harry Potter 5 in the cinemas: 11 July 2007. Hope it's correct since it's only from the stupid MSN website, also don't know for which country this date applies. Also found the 13th on IMBD, go there for the same trailer in English.

http://allocine.msn.fr/video/video_gen_cfilm=58608.html go here to see the trailer. It might be in French. Sorry ain't got no loudspeakers at Uni.