I very rarely trade in the pre- or after-market, so I would appreciate assistance on this: I tried to sell a long position at what I thought was right before the close on ARCA, but I was off by a few seconds, the time went past 4:00, and it got rejected because the order expiration type was "Day." OK, that makes sense. The strange thing was that I usually have a "Day +" order expiration type available for extended hours trading, but for some reason it didn't appear on the selection list. The only available types were Day, NOW, and GTC. So I ended up selling the position using a NOW order. I researched this on the web but all I could find was that NOW orders basically go to the Arca book and a "select group of market maker participants" for their best price which may or may not be the NBBO price. Strangely enough, after my order was filled, the "Day +" selection appeared again. I'm worried if a trade violation occured using the NOW order in the after market. I called my trading firm and they said that it was an order type I would never have to use, and they were surprised when I told them what happened. The guy I talked to wasn't sure about the NOW order and said he'd check into it. Being the end of the week, I probably won't hear from then until next week, so I'm hoping the bright minds here on ET will be able to clarify this for me. Also, I've never used a GTC order - can they be used in the after market? Finally, is there an order expiration type for Arca or ISLD routes that is valid for regular market hours as well as after and pre-market hours? Would GTC encompass all these time frames?