When it comes to eBay auctions, tiny details like when to end an eBay auction matters. For popular items such as laptops and Nintendo Wiis, it really does not matter when you end your eBay auction. You can end an auction at 5am in the morning, and you will still have buyers fighting over the item. There is literally a listing for each of these items ending every minute.
In general, for less popular items, the best time to end an auction is during the evening; between 9:00pm and 12:00pm EST. This has been proven to be the busiest time of the day for eBayers. People go online right after dinner and before heading off to bed to check their emails, Facebook, and browse the internet. This time span takes into account the timezone differences between the east cost and west coast. I personally end my auctions around 10:30pm EST.
The very best day to end the auction is on a Sunday. There have been many studies showing that Sunday evening is the busiest time on eBay.
With that said, there are also a few reasons why ending your eBay auction during this time can be a disadvantage. Other eBay sellers might be ending their auctions during this time as well since it is proven to be a busy time. Competition is not good for the sellers. The eBay market might be saturated with that item, and will drive the final price of the item down.
Also, know the audience that you are trying to sell to. If you are selling an item that is more popular to an older audience, you might want to experiment ending your auction between 9:30-11:30am since most older people will be at work. If you are trying to sell a video game targeted for teenagers, you might want to try ending your auction during the evening since teenagers tend to stay up very late at night or not sleep at all.:)
In addition, keep in mind that holidays are a bad time to end auctions since people go out of town during holidays, and have no access to computers. Another good tip is end your auctions a few minutes after:00,:15,:30, or:45. For example, if you want to end your auction at 10:30pm, end the eBay auction at 10:33pm instead. 10:30pm will have a higher chance of having another seller ending their auction at that time than at 10:33pm. Small details like these can get you those extra few dollars.