From 1999 up to about 2010 I listed only Auctions. I created new listings every day and over a period of 6 - 8 hours.
After more than 10 years of observation one thing because crystal clear........It did not matter one bit what day or what time an Auction ended. Good stuff sold for good prices regardless of the time and poor stuff didn't sell or didn't sell for a good price no matter what day or time it ended.
This was MY experience, it might not apply to other types of items or for sellers whose primary customer base is different from mine.
Things to consider......
Some people have plenty of time on a Sunday afternoon or evening while for others Sunday is a very busy day with lots of things to do that are more important than eBay Auctions.
If you sell Internationally, Sunday afternoon could be early morning or late evening for those buyers.
Some people do their eBay buying during working hours because their work involves sitting in from of a computer. Some people only shop at night because they work during the day and don't have access.
Some people sit around doing nothing much or watching TV on Sunday, some people give family a priority on the one day of the week when work etc.
There are so many variables it's very difficult to pick the "best" day/time, even harder to compare what works for one seller that will work for other sellers with a completely different customer base.
The only way to determine which is "best" is to run tests and analyze the results, even that is difficult unless you are selling the exact same (not just similar) items over and over again.
Now throw in the variables of buyers who bid at any time vs those who bid only in the last few minutes vs those that use snipping services that allow them to set up their bids at any time/day.
On the other hand, if you are selling stuff that appeals to a regional customer base, buyers who are of similar age/occupation/lifestyle you may have better luck trying to determine the optimum time.
I sell worldwide, my customers are mostly but not exclusively male and cover a wide age range but not so many teens or twenty somethings. What is a perfect time for my 55 year old customer in Germany could be the worst possible time for my 30 year old in California or my 18 year old in Australia.
