So when you buy an annual pass the first time, your year doesn't start until you use it the first time, but when you renew, it starts automatically? Is that the case?
Yes, even if you renew after your old AP expires your new AP expires one year from the expiration of the old one. AP renewals are discounted. Depending on your future trip timing it may be more economical to let your old one expire and buy a new AP later.