After you log onto disneyworld.com - there is an icon midway down on the left side marked "calenders" - they post the hours of the park then.
As for Night of Joy - I was told last year then had spectromagic the night before it started and then Tues of the weekend following. If you are going Sat to Sat - they usually try to get at least one in a week. From what I heard it is VERY crowded for that show so get a spot EARLY!! Even though the crowds are down in Sept, cramming everyone that is there for one week vacations into one show is tough. The economy is doing better and Disney is seeing increased numbers of guests since last year. I hope they increase Spectromagic to at least 2-3x a week to prevent the cramming. I also heard to not go to MK the whole day of Spectromagic. It is their busiest day of the week. If you have a hopper pass go to another park and then head over to MK at dinner.
I'm mostly concered with when Wishes and Spectro will run because our first Saturday there is Night of Joy and we will not be attending that.
Nights of Joy are supposed to be having fireworks everynight. Definately there last night which is Sat. If that is your first day and you are not going to any parks - you can watch the fireworks from the poly beach which is FUN and will get you in the disney mood!!!