Although Disney won't officially announce the dates until shortly before the tickets go on sale (which has typically been early May; last year was a change that may or may not continue), you can pretty much figure out what dates they'll take place. I doubt the first one will occur before November 8; for years now they've only been on Sundays, Tuesdays, Thursdays and Fridays; they don't have them the week of Thanksgiving; and the last one is typically a week before Christmas.