North American release date confirmed to also be on Sept 14th.

[BackRoomKid]

EDIT:
nevermind..looks like this is true...this is from www.square-enix.com

LOS ANGELES, California –May 15, 2005– Square Enix, Inc. (Square Enix) the publisher of Square Enix(TM) interactive entertainment products in North America, today announced the release date of the highly-anticipated, feature-length CG film, FINAL FANTASY(R) VII ADVENT CHILDREN(TM)(ADVENT CHILDREN). ADVENT CHILDREN will be released on September 14, 2005, in Japan, followed closely by a North American release.

but never found anything about a SPECIFIC date but seeing how a lot of official sites are confirming these dates...i doubt it'll be a long wait.

ANOTHER EDIT!!!
ok...looks like the september release date is a definete...the official english site says 117 days...in september something....don't feel like doing math