I have a June use year. We are currently in the June 2007 use year, which started June 1, 2007, and ends May 31, 2008. If I borrowed points from the use year that begins June 1, 2008, I would have to use those points for stays up to and including the night of, May 31, 2008.
If you borrow points from a June 1, 2010, use year, they would go into a June 1, 2009, use year, and have to used for stays upto and including the night of May 31, 2010.