I posted this in responce to a question about the 7 day pass upgrade policy. But as all upgrading is explained it should help.
The 7 day rule is you purchase a Hopper pass, use it for a few days , then decide to upgrade (in 7 days or less from purchase) to an AP, they will give you full credit (even for the days used) for the previously purchased Hopper pass towards the AP purchase and the AP will be dated the date of first use of the Hopper Pass. This makes it look like you just originally bought an AP on the day you bought the Hopper Pass. Upgrading an unused Hopper pass (fully unused) (bought more than 7 days previous) can be done anytime, they will credit the original purchase price towards the AP. The upgrade of a used Hopper pass (also bought more than 7 days previous) can also be done anytime they will prorate the remaining days at the original price towards the AP. In both of the last 2 upgrades the AP date will be the day of upgrade. They will upgrade a pass with 1 or 2 days remaining to a pass with a greater number of days using the same logic. I hope this makes sence...