You are allowed to trade from market open to market close, as long as the market is open! All trades must close by 4:15 pm EST, and you can reopen trades at 6:00 pm EST. You are free to trade overnight or at any time during the trading day, but you cannot trade during the 1 hour and 45-minute break between 4:15 pm EST and 6:00 pm EST, as the market is technically closed during this period. If you do not close your trade, don't worry! Your account won’t be breached. The trades will automatically close for you at 4:15 pm EST. So, you can relax, knowing your positions will be managed even if you forget to close them manually. :)