It is mid-day (I believe from 12noon to maybe 5pm EST). But the time of the drops is not the same, and never announced exactly. If it was, the number of folks and registers trying to slam the system with back-orders would send poor NeuStar (the .us registry) into a major overload crash of sorts and alot of bickering over mear milliseconds :lol:
Try a few of the back-order services like Pool.com, ExpireFish.com, GoDaddy.com, SnapNames.com, among others you'll find posted around here by searching for "back order" in the forums. They have systems (which you could too, but takes the money and skills) that can try over and over extremely fast till it either snatches the name on the drop or finds it taken by someone else.