A manufacturer can actually manufacture to a specific U.S. model year (MY) for up to 24 months, starting in January of the calendar year prior to the MY and up to december of the MY. However it is rarely done after mid-calendar year with a few exceptions. VW just did this with their 2006 MY Jetta Diesel because they couldn't yet meet the new emission standard that started with 2007 MY vehicles and they still wanted to sell diesel models in calendar year 2007 (manufactured up to December 2006).

It is now much easier in Europe, manufacturing calendar year = model year. Before, the MY change over occured in July...just my .02