A day order means that the futures order will only last for the duration of the days trading session. The order will expire and be cancelled at the close of trading for that day if it is not filled. By default, all orders are considered to be day orders unless you specify it as an open order.
An open order is the common term for an order that remains active until it is filled, cancelled or the contract expires. It is usually designated as a Good Til Cancelled or GTC order on most online trading platforms or the order tickets that a broker fills out.
Make sure to keep track of your open orders. Traders sometimes forget about them and get a nasty surprise down the road when an open order is filled. Stop orders are probably the most common open orders that traders forget about. It is a good idea to get into the habit of checking your open orders regularly.
