Yep, they do maintenance during that time. Sometimes they are up, sometimes down, sometimes a little of both. Since we cant tell which or when it's best that we just place them all a few seconds before 1am.
They used to do maintenance every week and always be down, thus there were always 0 items ending then because sellers couldnt list any items then. Now though they are up one week then down the next so it's quite possible items will be ending when eBay is down and bids wont be able to be placed. If it's know they'll be down it's actually decent time to get a good deal because other snipers are going to be locked out of bidding while yours will have went off before eBay goes offline. They usually announce on Wednesday afternoon if that we'll they're planning on being up down, or a little of both.