Direct Answer
Regular trading hours refer to a market's official session, for US stock exchanges, generally 9:30am to 4:00pm Eastern Time, during which the vast majority of trading volume and liquidity occurs. Extended-hours trading (pre-market and after-hours sessions) allows trading outside these hours, but typically with significantly lower liquidity, wider bid-ask spreads, and higher volatility. Because of this, a chart built from extended-hours data can show different price levels and patterns than the same chart restricted to regular-hours data only, so it matters which one the analyst is viewing.
Key Takeaways
- Regular hours are the official session. For US stock exchanges this is generally 9:30am to 4:00pm Eastern Time, and it is where the vast majority of trading volume and liquidity occurs.
- Extended hours are the add-on sessions. Pre-market and after-hours trading happen outside the official window and typically carry significantly lower liquidity, wider bid-ask spreads, and higher volatility.
- Charts can literally look different. A chart that includes extended-hours data can show different highs, lows, or gaps than the same period shown on a regular-hours-only chart.
- There's no single "correct" setting. Which data set is appropriate depends on what the analyst is trying to do, there is no universally correct answer for every situation.
- Consistency matters more than the choice itself. Switching between the two settings without noticing can make support/resistance levels and patterns appear to shift for no real reason.
What Are Regular and Extended Trading Hours?
Every exchange runs on an official session. For US stock exchanges, that regular session is generally 9:30am to 4:00pm Eastern Time, and it is where the vast majority of a stock's trading volume and liquidity occurs. Most participants, institutional order flow, market makers actively quoting both sides of the market, and the bulk of retail activity, are concentrated in this window. That concentration of participants is what makes regular-hours prices the default reference point for closing prices, daily statistics, and most charting defaults.
Extended-hours trading covers the pre-market session (before the regular open) and the after-hours session (after the regular close). These sessions allow trading outside the official window, but they typically come with significantly lower liquidity, wider bid-ask spreads, and higher volatility than the regular session. Fewer participants are active, order books are thinner, and a comparatively small order can move the price more than an equivalent order would during the regular session.
These two facts, where most volume happens, and how much thinner the surrounding sessions are, are the basis for why regular-hours and extended-hours data can produce genuinely different pictures of the same stock over the same calendar period.
Why the Two Data Sets Can Diverge
A candlestick chart is a summary of trading activity over a period, and it is only as representative as the activity that fed it. When a chart includes extended-hours data, the candles for a given day can incorporate price moves from pre-market or after-hours trades that never happened during the regular session at all, for example, a stock reacting to an earnings release published after the regular close. When the same chart is restricted to regular-hours data only, those extended-hours price moves are excluded, and the day's high, low, open, or close can come out differently.
Because extended-hours activity happens with lower liquidity, it can also be more prone to sharp, short-lived price swings that don't necessarily reflect where the stock trades once the regular session's deeper pool of participants resumes. Support and resistance levels, trendlines, gaps, and chart patterns identified on an extended-hours chart may not line up with the same analysis performed on a regular-hours-only chart of the same security.
Hypothetical Example, For Education Only
Consider a hypothetical stock that closes the regular session at $50.00. After the close, the company releases better-than-expected earnings, and in after-hours trading the stock changes hands as high as $54.00 on relatively light volume before settling back toward $52.00 by the end of the after-hours session. The next morning, in the pre-market session, the price drifts to $51.50 before the regular session opens.
On a chart that includes extended-hours data, that after-hours spike to $54.00 would appear as part of the price record for that day, and the next day's candle might reflect an open near $51.50. On a chart restricted to regular-hours data only, the $54.00 spike and the pre-market drift would not appear at all, the record would simply show the $50.00 regular-session close followed by whatever price the stock opens at once the next regular session begins at 9:30am Eastern. The same underlying event produces two visibly different charts, neither of which is "wrong", they are simply built from different data.
How to Apply This
- Check your charting platform's default setting. Many platforms default to regular-hours-only data, but some include extended hours by default or offer a toggle, know which one you're looking at before drawing conclusions from a chart.
- Be consistent when comparing periods. Switching a chart's setting between regular-hours-only and extended-hours-inclusive mid-analysis can make levels appear to move for reasons that have nothing to do with the stock itself.
- Treat extended-hours price action with extra caution. Because these sessions typically carry significantly lower liquidity, wider bid-ask spreads, and higher volatility, a single sharp extended-hours move may not carry the same weight as a comparable move during the regular session.
- Match the data set to the question being asked. There is no universally correct choice, an analyst focused on how a stock reacted immediately to overnight news has a different reason to look at extended-hours data than one drawing a longer-term trendline from regular-session closes.
A Level Can Exist on One Chart and Not the Other
The consequence that catches people out is that a session setting changes the chart itself. A pre-market spike that becomes the period high on an extended-hours chart simply does not appear on a regular-hours one, so a resistance level derived from it exists for one analyst and not another looking at the same instrument on the same day. Neither chart is wrong, and they will disagree about where price has been rejected.
Gaps behave the same way. A move that happened between the close and the next open shows as a clean gap on a regular-hours chart, and on an extended-hours chart it may be filled in by thin overnight trading, which changes whether the pattern is a gap at all.
That is why the setting belongs in any note about a level. Saying resistance at a given price is incomplete without saying which session data produced it, particularly when the level came from a period around an announcement.
Also weigh the extended-hours prints for what they are. Those sessions carry far less volume, wider spreads and larger swings, so a level set by a handful of trades outside the main session is evidence of a different quality from one established across a full day of liquid trading.
FAQ
What are regular trading hours for US stocks?
Regular trading hours refer to a market's official session, which for US stock exchanges is generally 9:30am to 4:00pm Eastern Time. This is the session during which the vast majority of trading volume and liquidity occurs, and it is the session most quote systems, charting defaults, and closing-price references are built around.
What is extended-hours trading?
Extended-hours trading refers to the pre-market and after-hours sessions that allow trading outside a market's official regular-hours window. These sessions typically have significantly lower liquidity, wider bid-ask spreads, and higher volatility than the regular session, since far fewer participants and far less order flow are active.
Why is extended-hours trading riskier than regular-hours trading?
Extended-hours sessions typically have significantly lower liquidity than the regular session, which generally means wider bid-ask spreads (a larger gap between what buyers will pay and sellers will accept) and higher volatility (larger, faster price swings on comparatively small orders). With fewer participants providing quotes, a single trade can move the price more than the same-sized trade would during regular hours.
Does extended-hours data change how a stock's chart looks?
Yes. Technical analysis conducted on charts that include extended-hours data can show different price levels and patterns than charts restricted to regular-hours data only. A chart including extended hours may display different highs, lows, gaps, or candlestick shapes than the same period shown on a regular-hours-only chart, because the extended sessions add price action from a thinner, less representative pool of trading activity.
Should I include extended-hours data in my technical analysis charts?
There is no universally correct answer. What matters most is that the analyst knows which setting their chart is using and applies it consistently, since support/resistance levels, trendlines, and pattern recognition identified on an extended-hours chart may not line up with the same analysis performed on a regular-hours-only chart of the same security.
Can I place trades during pre-market or after-hours sessions?
Many brokers offer access to pre-market and after-hours sessions, generally with order-type restrictions and the lower-liquidity, wider-spread, higher-volatility conditions typical of extended hours. Specific hours, eligible order types, and trading rules vary by broker, so confirm the current policy with your broker before trading outside the regular session.
Do extended-hours prints count toward the day high and low?
That depends on a setting, and both behaviours are common. Including them widens the bar, which changes the recorded range and therefore every indicator computed from it, including average true range and any level derived from a prior high or low. The chart gives no indication of which convention is in force, so a level that appears to have held on one chart can appear broken on another.
Does including extended hours make gaps disappear?
It can. A gap on a regular-hours chart is the space between one session close and the next session open, and if the overnight session traded through that space then a chart including it shows continuous price instead. The move happened either way. Whether it is displayed as a gap is a charting choice, which matters for any rule that references gaps as events.
Is extended-hours volume comparable to regular-session volume?
No. It is a small fraction of the daily total, concentrated in a limited number of names and in the minutes around news. Volume-based indicators computed on a chart that includes it therefore see a long tail of very low readings that do not mean the same thing as a quiet regular session. Comparing an extended-hours volume figure against a regular-hours average compares two different things.
References
Disclaimer
This article is for educational and informational purposes only and does not constitute personalized investment, financial, or legal advice. Session hours, liquidity conditions, and broker rules for extended-hours trading can vary and change over time, always verify current details with your broker or exchange. Trading involves risk, including the possible loss of principal.