Well I'm all for the birthday being july 17th. But the question I have for everybody is, when a ride soft opens for a month before its official "Opening Ceremony," when is the ride's birthday? If a movie is shown to the film academy, news reporters, and guests invited to preview the film, all prior to the official release date, when was the movie released?
The only reason I want to count July 17th in this instance is because it seemed much more of a premiere event than a preview. All of the dedications and formal opening ceremonies took place on this day, and it seems illogical to have plaques on the Mark Twain declaring its anniversary to be July 17th if that predates Disneyland's anniversary. There's a difference between unveiling something and having an opening.