Your schedule change was sufficient enough to warrant rebooking, but as others have said, you may not have luck with changing the date. I had a situation, albeit a domestic trip, where the Tuesday morning nonstop to LGA from MKE schedule changed to about 2 hours later. That meant that I would be arriving work more than just a little bit late. I called up and simply asked to be put on a MSN-MSP-LGA routing the night before, and they did it without question. Never hurts to ask and it never hurts to hang up and try again!