I think that depends first off on your time zone.
I'm on the East coast. I find that listing my items at approximately 10pm (+/- 15 minutes) is a good time to be conveniently viewed in all four time zones. Not too late (east) not too early (west).
Another thing to keep in mind is people may be using snipe bidding services which then make time irrelevant. I always use eSnipe for bids, and then just forget about the item, and either win or loose.
I also find Sundays & Mondays to be good days, but really, any day other than Saturday is good. But then again, with the use of sniping programs, the day become irrelevant too.