Normally I start checking after 9 pm the night before since cancellations seem to flood in before 12 midnight.
Like DLGal mentioned early AM works too but once they're gone [on same day] that's it unless Disney changes programing since you can't cancel same day. Those guests will just get a 'no show' if they don't go to parks.
Pretty much the only other time I've seen days stay open all day is in bad weather, or random slow day (very rare)
Our Authorized Disney Vacation Planners are here to provide personalized, expert advice, answer every question, and uncover the best discounts.
Let Dreams Unlimited Travel take care of all the details, so you can sit back, relax, and enjoy a stress-free vacation.