There needs to be a clarification on this.
Unlike regular tickets that DO "self-activate" when you enter the park with them the first time...
AP tickets will be activated "manually" when a guest goes to a
Guest Relations or ticket booth to pick up a new "live AP" for the first time.
That means that if a guest goes to pick up a new AP on, say, Dec. 22, 2014, but does not enter a theme park with it until, say, Dec. 26, 2014, the AP will still have become "active" on Dec. 22, 2014 and will be valid until (and on) Dec. 22, 2015...
regardless of the date the AP was first actually USED to enter a park.