The runs October 15 through December 7. Anything you change takes effect January 1.
You do not need to do anything on October 15. What you do need is to have read your Annual Notice of Change before then — it arrives in September, it looks like junk mail, and it tells you exactly what your plan is changing for next year.
If either answer is no, that is the year to look at your options — and the window to do it closes December 7.
