Is the stock market open 24 hours? Futures sessions and backtests
US stock exchanges are not open 24 hours, but index futures such as ES and NQ trade nearly 23 hours a day. A futures backtest must state which hours its bars cover and must price the thinner overnight market realistically.
By Soren Huang · Published · updated · Editorial policy
Contents
- Is the stock market open 24 hours?
- Why is 24-hour stock trading not the same as ES and NQ futures sessions?
- How do overnight sessions change gaps, volume and daily bars?
- Gaps
- Volume
- Daily bars
- Which session should your backtest include?
- How much extra slippage should you assume overnight?
- Frequently asked questions
No. US stock exchanges hold regular trading from 9:30 a.m. to 4:00 p.m. Eastern time on weekdays, with pre-market, after-hours and some broker overnight sessions around it. Index futures such as ES and NQ trade nearly 23 hours a day, Sunday evening to Friday afternoon. So a backtest must state which hours its bars cover and what overnight fills cost.
Is the stock market open 24 hours?
The main US stock exchanges are not open 24 hours. Nearly round-the-clock trading is normal for futures, currencies and crypto, not for listed stocks. A trading session is a block of hours during which a market accepts and matches orders. Most markets have several sessions per day, and the gaps between them matter in a backtest.
| Market | Hours (local exchange time) | Daily break | Weekend |
|---|---|---|---|
| US stocks, regular session | 9:30 a.m. – 4:00 p.m. ET, Monday to Friday | Closed from 4:00 p.m. until the next morning, apart from extended hours | Closed |
| US stocks, extended hours | Before 9:30 a.m. and after 4:00 p.m. ET; exact times depend on the broker | Depends on the broker | Closed |
| US stocks, broker overnight trading | Overnight on weekdays for a selection of stocks and ETFs; hours set by the broker | Depends on the broker | Closed |
| CME equity index futures (ES, NQ, MES, MNQ) | 6:00 p.m. ET Sunday to 5:00 p.m. ET Friday | 5:00 – 6:00 p.m. ET every weekday | Closed from Friday 5:00 p.m. to Sunday 6:00 p.m. ET |
| TAIEX futures (TAIFEX) | Day 8:45 – 13:45; night 15:00 – 05:00 next day (Taiwan time) | 13:45 – 15:00 and 05:00 – 08:45 | Friday's night session ends Saturday 05:00 |
| Crypto | 24 hours, 7 days a week on most venues | None | Open |
For readers in Taiwan, the CME daily break falls at 5:00 – 6:00 a.m. Taiwan time while the US is on daylight saving time, and at 6:00 – 7:00 a.m. in the US winter. Exchanges can change their trading hours, so check the exchange's contract page before you set up a test. The free futures market hours tool shows each session in your own time zone.
Why is 24-hour stock trading not the same as ES and NQ futures sessions?
Overnight stock trading and overnight futures trading look similar on a clock, but they are different markets with different data.
| Aspect | Overnight stock trading | ES and NQ futures |
|---|---|---|
| Where the trades happen | Usually through a broker on an alternative trading system, not on the stock's main exchange | One central exchange order book for the whole session |
| Which instruments | Brokers that offer "24/7 stock trading" usually mean 24 hours on five weekdays, and only for a chosen list of stocks and ETFs | A futures contract trades through every session for which it is listed |
| Order types | Brokers often accept only limit orders overnight | The same order types day and night |
| The index itself | The S&P 500 and Nasdaq-100 index values are calculated from stock prices during regular stock hours, so they stay at their last value overnight | ES and NQ keep trading and react to news from Asia and Europe |
| Historical data | Check whether your historical data includes overnight stock trades at all | Futures data vendors normally offer full-session bars |
For a side-by-side view of cash and futures hours, see US stock market hours vs futures sessions.
How do overnight sessions change gaps, volume and daily bars?
Including or excluding the overnight session changes the price series your strategy sees, so it changes the signals. Three effects matter most.
Gaps
A gap is the jump between one bar's close and the next bar's open when no trades took place in between. On a chart that shows only day-session bars, the whole overnight move appears as one gap at the open. On a full-session chart, the same move is spread across many overnight bars. The weekend break and the one-hour daily break still create real gaps. The Sunday 6:00 p.m. ET open is where weekend news shows up.
Volume
ES and NQ volume is concentrated in US regular hours. Overnight volume is lower, with short bursts around the European open and scheduled news, such as US economic reports often released at 8:30 a.m. ET. A volume filter tuned on regular-hours bars will behave differently on overnight bars.
Daily bars
A full-session daily bar for ES runs from 6:00 p.m. ET the evening before to 5:00 p.m. ET. A day-session daily bar covers roughly the cash market hours. The exact start and end depend on the session template, which is the set of session times your data or platform uses to build bars. The two daily bars have different opens, highs and lows, so any rule built on them gives different results.
Hypothetical example
ES closes the day session at 5,000. Overnight it trades up to 5,040, down to 4,990, and sits at 5,035 when the day session opens. On a day-only chart, the next day opens with a 35-point gap, and the overnight high and low of 5,040 and 4,990 never appear. On a full-session chart, there is no gap, and the daily range includes those overnight prices. A strategy with a stop at 4,995 would show no stop-out on the day-only chart. On the full-session chart, the stop is hit overnight.
Indicators that use the daily range, such as the Average True Range (ATR), give larger values on full-session bars than on day-only bars. Stop distances and position sizes based on ATR change with them.
Which session should your backtest include?
Backtest on the same session template you will use live, and include every hour in which your position is open. If the backtest and the live chart build bars from different hours, the signals will not match, even with identical rules.
| How you trade | Session to test | Why |
|---|---|---|
| Intraday, regular hours only, flat before the close | Day session, or full-session data with entries limited to regular hours | The position never sees the overnight market. Decide whether indicators should still use overnight bars, and keep that choice the same live. |
| Holding positions overnight | Full session | Stops and targets can be hit at night. Day-only bars move those fills to the next open. |
| Trading the overnight session itself | Full session, with costs set for thin hours | Fills and spreads at night differ from those in the day session. |
| Daily-bar strategies | One daily bar definition, used in both test and live trading | Full-session and day-session daily bars have different opens, highs and lows. |
Set up the test in this order:
- Write down the hours in which the strategy may enter and the hours in which it may hold a position.
- Choose the data series: day session or full session, with the exchange's time zone stated.
- Check that your live platform will use the same session template.
- Set fees, slippage and next-bar execution before the first run.
- Run the test once on the other session template as a comparison. A strategy that only works on one template may depend on how its bars are built.
AlphaPrime (Valynox) includes trading sessions, data resolution, next-bar execution, and fees and slippage in its backtesting settings, so the session choice is part of every evaluation. For TAIEX futures, the same decision is covered in night sessions in futures backtests: day-only vs. full-session bars.
How much extra slippage should you assume overnight?
Assume more slippage for overnight entries and exits than for regular hours, because there are fewer orders in the book at night. Slippage is the difference between the price the backtest assumed and the price you actually get. In a thin market, a market order or stop order has to reach further into the order book to fill, and the bid-ask spread is often wider.
- Use your own fills. If you have live history, group fills by hour and compare them with the signal price.
- Without live history, add a margin. Use at least one tick per side as the base, and assume more for overnight entries, for stop orders, and for minutes around scheduled news.
- Stress test. Rerun the backtest with double slippage. If the result turns negative, the edge depends on cheap fills.
- Check when the trades happen. If most entries fall in thin hours, test a version that only enters in regular hours.
Hypothetical example
An ES strategy averages $40 per trade after normal costs. One ES tick is 0.25 points, worth $12.50. Suppose 60% of its trades enter and exit overnight, and you add one extra tick of slippage on each side for those trades. That costs $25 per overnight trade, or $15 per trade across all trades. The average trade falls from $40 to $25. If doubled slippage pushes it near zero, the strategy depends on overnight fills it may not get.
The full method for comparing the average trade with its costs is in trading costs in backtests: commission, slippage and the average trade.
What this means if you use AlphaPrime: choose the session and the slippage that match how you will trade before you start a search. The candidates are then ranked on the hours and costs you will actually face. Afterwards, look at the trade list and periodic results in the Performance Report to see when the strategy makes and loses money.
Frequently asked questions
Is the stock market open 24/7?
No. US stock exchanges trade on weekdays, with a regular session from 9:30 a.m. to 4:00 p.m. Eastern time plus pre-market and after-hours sessions. Some brokers offer overnight trading in selected stocks and ETFs, but usually only on weekdays. Crypto is the main market that trades every day of the week.
Can you trade stocks 24 hours a day?
Some brokers let you trade a selection of US stocks and ETFs overnight on weekdays, often with limit orders only. These trades usually run on alternative trading systems, not on the stock's main exchange. Liquidity at night is lower than in the regular session, so spreads are often wider.
When do ES and NQ futures stop trading each day?
CME equity index futures such as ES and NQ trade from 6:00 p.m. ET Sunday to 5:00 p.m. ET Friday. On each weekday they pause from 5:00 to 6:00 p.m. ET. In Taiwan, that break is 5:00 to 6:00 a.m. during US daylight saving time and 6:00 to 7:00 a.m. in the US winter.
Should I backtest futures with day-session or full-session data?
Use the session you will trade live and cover every hour in which a position is open. If you hold positions overnight, use full-session data, because stops can be hit at night. If you trade only in regular hours and close before the end of the day, day-session data or full-session data with limited entry hours both work, as long as your live chart uses the same choice.
What AlphaPrime does here
AlphaPrime's backtesting evaluates every strategy with your chosen trading sessions, fees, slippage and next-bar execution. The Performance Report shows equity, drawdown, individual trades, periodic performance and long and short analysis.