[I tried to post this and the website refused to cooperate. I'm posting it now because it's all typed and ready. OP might not need it at this point, though.]
I think of it like a Fiscal Year. Your Fiscal Year starts March 1 each year and ends February 28 of the following year. You get your allotment of points on the first day of each Fiscal Year.
If you want to book a trip which starts on September 15, 2018 (as an example): if you will be staying at your Home Resort, you can start booking on October 15, 2017. If you will be staying somewhere other than your home resort, you can start booking on February 15, 2018. You will be traveling in the Fiscal Year which starts March 1, 2018. When you book that vacation, you can use the points which you will receive on March 1, 2018. If that's not enough, you can borrow some or all of the points which you will receive on March 1, 2019.
If that's too confusing, just ignore this!