I synch the OwnerRez calendar with AirBnB. On Memorial day I had an opening but my calendar in AirBnB showed "Memorial Day" as blocked. It turns out that Memorial Day from OwnerRez was passed through iCal as blocked to the AirBnB calendar. My AirBnB to OwnerRez synch then showed "Memorial Day" as blocked on my OwnerRez calendar. Not sure if this makes sense, but I think this is what happened.
Can you send me the OwnerRez property id and the Airbnb iCal link? I'll have a look.
Air has a bad habit of including rules like arrival days or days in advance in their calendar feeds as blocked off time.