There have been statistics released that show the greatest amount of traffic on Sunday nights. That is the easy answer.
I have personally looked into this issue quite a bit and kept track of personal sales statistics. I have found that it doesn't make much of a difference. The reason for this is because the times when there are the most buyers are simultaneously the times when there are the most items for sale.
There are ways of taking advantage of certain supply and demand shifts. Most people list things for 7 days. Sometimes, the listing day/time will be a normal day, yet the finish day/time will be unusually high or unusually low. Many sellers don't always pay enough attention to such things when listing. I mistakenly listed some coins ending exactly during one of the presidential debates because a week earlier I didn't look up the time. Many other sellers did too. The supply was the same, yet the demand was reduced due to people watching the debate. I took a beating on those coins.
When selling, always look at what's going on when something ends.
Never list, if anything special is going on that finish day. If you have the time, it could also work out well if you listed on a day when something big is happening. Most other sellers won't, yet a week later the buyers will be there.
Take the super bowl. A great day to buy coins and to begin listings. Nobody else is buying and nobody else is selling although a week earlier and a week later things were essentially normal.
Edited by hesgut
11/17/2012 9:28 pm