I think that most people get on their computer after work/dinner, so 8-9 EST or later, and then any time after that for people in central, west and farther. But then again it depends on your clientele, if they're going to come to your shop anyway, it probably doesn't matter when you list. I get alot of views in the daytime hours, and less at night, so if you find a similar trend, you could try listing when your views are highest.
I've been told there is no formula, so if you list at a certain time and get sales, try it again!