I notice that I can always see new movies here on the west coast a day early starting at 9 PM because of the time zone I'm in.
I.E. a nationwide release starts 12:00 AM (midnight) on Thursday EST. At that time theaters here on the west coast start playing at the same time which is 9:00 PM Wendsday PST.
I don't know if this is legal or if the theatres are cheating or splitting hairs, but I can say it does happen on a regular basis.