Approximately true, but...
If you merely PURCHASE an AP, the date is irrelevant (except for making advance FP+ reservations, which can be done using only a purchased, but unactivated AP certificate.)
It's only the date that you ACTIVATE that AP that matters concerning the useful life of the AP.
An AP can only be activated in-person at WDW.
(And, yes, you CAN purchase and activate the AP on the same date, if you are physically at WDW to do so.)