More to the point, rather than this being a battle of opinions, I think the issue is more definitional. One person might go to AK from 8:00 a.m.-4:00 p.m. and say that they "spent pretty much the whole day there." Another person might arrive and depart at exactly the same time and say that they "spent half a day there." When people talk about a park being a "half day park", I don't think they mean that they arrive at 9:00 and leave at noon. So instead of using the colloquial term "half day park", we would all be better served if folks were more specific in stating how many hours they typically spend touring a particular park. If someone posts that they are in and out of AK in 7 hours, one might consider that to be a full day and others might consider it to be a half day. But at that point, the terminology is irrelevant because we are all on the same page as to how many hours that particular family spent in the park.