You can book your home resort using home resort points 11 months prior to check in regardless of your Use Year. You can book any resort using any points 7 months from check in regardless of your UY. As disneynutz said, your UY determines when your annual points renew each year and also your banking deadlines but has no effect on when you can book a stay. It also determines which UY's points can be used for your trip. For example:
With a February Use Year:
Your Feb 2009 points are valid for stays from 2/1/2009 to 1/31/2010
Your Feb 2010 points are valid for stays from 2/1/2010 to 1/31/2011
Your Feb 2011 points are valid for stays from 2/1/2011 to 1/31/2012
and so on until the end of your contract.
If you want to book a trip for March 2010, your Feb 2010 points are valid for your travel dates. You could also use Feb 2009 points that had been banked into your Feb 2010 Use Year (provided they had been banked by the banking deadline: Sep 30, 2009). You could also borrow points from your Feb 2011 UY into your Feb 2010 UY to book that trip. But no matter which points you use, you could have booked that stay in Apr 2009 if booking your home resort using home resort points or in Aug 2009 if you were booking Resort A using points from Resort B.