It is normally one hour before scheduled opening and up to three hours (although I've never seen anything except three) after scheduled closing. In fact, it still says this on their EMH page. However, park hours differ depending on the time of year, so you have to check the scheduled park hours when you will be there to determine when EMH will be. And they are subject to change (and lately have been being changed at the last minute). And so are the EMH days.
For example, Wed Jun 10, at AK, regular park hours are 9-7, and EMH are 8-9 in the morning.
The best thing to do, I think is to check the official web site
http://disneyworld.disney.go.com/calendars
(or go by the weekly schedule handed out when you check in).
Another good source with a neat interface is
http://www.wdwinfo.com/wdwinfo/hours.htm
but I have noticed that it conflicts with the official site sometimes, and It's hard to be sure which is correct.
As advised in the Unofficial Guide (one of my favorite resources), call 407 824 4321 to hear official up-to-the minute park hours, and call back the day before you go to make sure.
And I believe that they are not doing wristbanding at any of the parks right now - you have to show your resort ID. Other posters can correct me if I am wrong, but that is the latest I heard.
...by the way AK only offers emh hour in the morning for one hour, and one hour sometimes in the evening (well it did whilst we were there for 14 days,just got back)
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