When I looked into this, it seemed that expats could actually extend their filing deadline to a date that is 12 months after their move so that they would qualify for a full year of residency! The extension form allows you to fill in a specific date of your choosing.
Here we go, I found it:
You can get an extension of more than 6 months to file your tax return if you need the time to meet either the bona fide residence test or the physical presence test to qualify for either the foreign earned income exclusion or the foreign housing exclusion or deduction. The tests, the exclusions, and the deduction are explained in chapter 4.
You should request an extension if all three of the following apply.
1. You are a U.S. citizen or resident.
2. You expect to meet either the bona fide residence test or the physical presence test, but not until after your tax return is due.
3. Your tax home is in a foreign country (or countries) throughout your period of bona fide residence or physical presence, whichever applies.
If you are granted an extension, it generally will be to 30 days beyond the date on which you can reasonably expect to qualify under either the bona fide residence test or the physical presence test. However, if you have moving expenses that are for services performed in 2 years, you may be granted an extension to 90 days beyond the close of the year following the year of first arrival in the foreign country.
http://www.irs.gov/publications/p54/ch01.html#d0e560The form for this is 2350