The tickets typically go on sale May 1st, and I believe they'll officially announce dates shortly before that. However, park hours for October will be released mid to late March, and you'll be able to tell what dates the party will take place because MK closes at 7:00 on those dates. Also, Sundays, Tuesdays, Thursdays and Fridays are good bets for party dates, except for Columbus Day week, when they'll most likely have a party on Monday, but not on Sunday or Tuesday.