Episode and/or Event end times

(Do we really not have an issue for this already? I searched...)

We need end times either on episodes or events (or both). My main motivation for this is so that stats don't look stupid if you look at them months later, but it would also mean we can automatically stop accepting guesses, display a "These r winners" screen and so on, and we don't have to take the site offline or anything, so people can look at whatever we put there after the Hunt is over.

There is a question over what exactly counts as the "end time". Typically at iHunts we declare the winners and go get dinner at 8PM or something when a few teams are still going. Basically for race-type iHunts it doesn't matter if the end time is even days later. But if we are going to support giving out other prizes based on completion rates or something, then the end time has to be strict and stop allowing guesses, or stop allowing them to count. The reason this is important is for display: if the hunt "ends at midnight on Sunday" but the winner is declared at 8PM or something, it seems a bit poopy maybe?