The stock market’s regular trading hours are from 9:30 a.m. to 4:00 p.m. Eastern Standard Time. There are is also a pre-market session every day from 4:00 a.m. to 9:30 a.m. EST and a post-market session from 4:00 p.m. to 8:00 p.m. EST Check the NY Stock exchange’s website for hours and holidays.
The regular trading session from 9:30 a.m. to 4:00 p.m. is the typical market session that most people refer to as the “day’s trading session”. This is when the vast majority of the day’s volume transacts and when most market participants are active. Because there is more volume posted to stock’s books during the regular session it is arguably more predictable and a safer time for day traders to be involved due to the higher likelihood of having liquidity available to execute orders. Some day traders prefer pre-market or post-market sessions however and only trade these times. Generally it is recommended that only experienced traders participate in the extended hour’s sessions however due to the possibility of extreme volatility.
Some stocks are very active in the pre-market and post-market sessions, and some have no activity at all. The spread will often widen significantly at non regular session hours and it can be very difficult to enter and exit large positions.
It is very important for a trader to understand the stock they are trading and the likelihood of liquidity being available after the closing bell. If a trader accidentally does not exit a position by 4:00 p.m. it can be very tough to exit after the close, and with a wider spread significant price slippage can occur. This can needlessly cost a trader a lot of money.
Only experience can give a trader a feel for the differences; but it is crucial to understand the differences between sessions and the differences between how particular securities trade during these times. Always trade a light position until you understand the risks and movements of the hours you are trading.