It IS a year plus a day. If it was 365 days, it would be a date one date less than the date you first used it, but Disney lets you go in on the expiration day, so they give you 366 days instead of 365.
Thanks everyone. Looks like we're using the PAP 05-23 to 05-26 for our OKW stay. Then when it expires heading to Vero Beach on 05-27 for four days. Can't beat a WDW stay combined with the beach!