When can I trade?
Orders to buy or sell will only execute during market hours.
However Out of Hours, Limit and Stop Orders can be placed and queued at any time but will only be executed during market hours and when the conditions of the order are met.
For US stocks, the largest marketplaces are the New York Stock Exchange (NYSE) and NASDAQ (based in New York City) which have normal trading hours of 9:30a.m. to 4.00p.m (Eastern Standard Time), unless there's an early close due to a holiday.