US stock market hours in Central Time: CST, CDT and bar data
The US stock market's regular session runs 8:30 a.m. to 3:00 p.m. Central Time in both CST and CDT. Only the offset from UTC changes, so a backtest has to know which clock its bars use and convert by date, not by a fixed number of hours.
By Soren Huang · Published · updated · Editorial policy
Contents
- What are the stock market hours in Central Time?
- CST or CDT: which label is correct?
- When do equity index futures trade on CME Globex in Central Time?
- How do you convert Central Time to UTC, Taiwan and London time?
- Which time zone should your bar data use?
- What does this mean for testing a strategy?
- Frequently asked questions
US stock market regular hours are 8:30 a.m. to 3:00 p.m. Central Time, Monday to Friday, in both winter (CST) and summer (CDT). CME equity index futures trade from 5:00 p.m. to 4:00 p.m. CT the next day. In UTC and Taiwan time, these hours move by one hour twice a year.
What are the stock market hours in Central Time?
The NYSE and Nasdaq regular session is 8:30 a.m. to 3:00 p.m. Central Time, Monday to Friday, except on exchange holidays. Regular trading hours are the main session in which the opening and closing auctions take place and most volume trades. The exchanges publish these hours in Eastern Time as 9:30 a.m. to 4:00 p.m. ET. Central Time is one hour behind Eastern Time all year, so this conversion is always one hour.
Pre-market and after-hours trading, together called extended hours, can run from 3:00 a.m. to 8:30 a.m. CT and from 3:00 p.m. to 7:00 p.m. CT at the widest. Your broker's window may be shorter.
On some days the NYSE closes early, at 1:00 p.m. ET, which is noon CT. The day after Thanksgiving is the best-known example. The stock market holidays and early closes calendar lists the exact dates for each year.
| Session | Central Time (CT) | Eastern Time (ET) |
|---|---|---|
| Pre-market (widest exchange window) | 3:00 a.m. – 8:30 a.m. | 4:00 a.m. – 9:30 a.m. |
| Regular trading hours | 8:30 a.m. – 3:00 p.m. | 9:30 a.m. – 4:00 p.m. |
| After-hours (widest exchange window) | 3:00 p.m. – 7:00 p.m. | 4:00 p.m. – 8:00 p.m. |
| CME Globex equity index futures | 5:00 p.m. – 4:00 p.m. next day, Sunday to Friday | 6:00 p.m. – 5:00 p.m. next day |
| Globex daily break | 4:00 p.m. – 5:00 p.m. | 5:00 p.m. – 6:00 p.m. |
Exchanges can change these hours. Check the exchange's own hours page or the futures contract page before you rely on them. The futures market hours tool shows each session in your own time zone.
CST or CDT: which label is correct?
Use "CT" for the session hours and a named time zone for your data, because CST is correct only in winter and is also used for other zones. CST (Central Standard Time) is Chicago's winter clock, at UTC−6. CDT (Central Daylight Time) is Chicago's summer clock, at UTC−5. UTC (Coordinated Universal Time) is the world reference clock, and it never changes for daylight saving.
Daylight saving time is the practice of moving the clock one hour forward in spring and back in autumn. In the US, it starts on the second Sunday in March and ends on the first Sunday in November, at 2:00 a.m. local time. The exchanges set their hours in US local time, so the session stays at 8:30 a.m. to 3:00 p.m. on the Chicago clock in both seasons. Many people search for "stock market hours CST" in July, but in July Chicago is on CDT.
The bigger problem is that "CST" is not unique. The same three letters are also used for China Standard Time (UTC+8, the same offset as Taiwan) and for Cuba Standard Time. A data file or chart header that says only "CST" can mean a 14-hour difference. Software time zone libraries avoid this with named zones. America/Chicago is the name for Chicago time, and it switches between CST and CDT on the correct dates. Asia/Taipei is Taiwan time, which has no daylight saving.
When do equity index futures trade on CME Globex in Central Time?
E-mini and Micro equity index futures, such as ES, MES, NQ and MNQ, trade from 5:00 p.m. CT on Sunday to 4:00 p.m. CT on Friday, with a break each day from 4:00 p.m. to 5:00 p.m. CT. Globex is CME Group's electronic trading platform. CME is based in Chicago, so its data and charts are often shown in CT, and its trading day starts in the evening: the futures "Tuesday" begins at 5:00 p.m. CT on Monday.
The US clock change happens at 2:00 a.m. on a Sunday, before the Globex week opens at 5:00 p.m. CT. In exchange time, no session is shortened or lengthened by the change. In UTC, the Sunday open moves from 23:00 in winter to 22:00 in summer.
How a stock-session test should cut the futures day, and how full-session and day-session bars differ, is covered in the guide to US stock market hours vs futures sessions.
How do you convert Central Time to UTC, Taiwan and London time?
Convert by date, not by a fixed number of hours, because the gap between Chicago and other cities changes up to four times a year. Taiwan stays at UTC+8 all year. London moves to summer time on the last Sunday in March and back on the last Sunday in October. These dates differ from the US dates, so for a few weeks each spring and autumn London is five hours ahead of Chicago instead of six.
| Period | Chicago clock | Regular session in UTC | Regular session in Taiwan time | 8:30 a.m. CT open in London | Globex break in UTC |
|---|---|---|---|---|---|
| First Sunday in November to second Sunday in March | CST, UTC−6 | 14:30 – 21:00 | 22:30 – 05:00 next day | 14:30 | 22:00 – 23:00 |
| Second Sunday in March to last Sunday in March | CDT, UTC−5 | 13:30 – 20:00 | 21:30 – 04:00 next day | 13:30 | 21:00 – 22:00 |
| Last Sunday in March to last Sunday in October | CDT, UTC−5 | 13:30 – 20:00 | 21:30 – 04:00 next day | 14:30 | 21:00 – 22:00 |
| Last Sunday in October to first Sunday in November | CDT, UTC−5 | 13:30 – 20:00 | 21:30 – 04:00 next day | 13:30 | 21:00 – 22:00 |
Two things in this table catch traders in Taiwan. First, the US regular session closes on the next calendar day in Taiwan time, so one US trading day spans two Taiwan dates. A daily bar built on Taiwan dates splits that session in two. Second, a trader in London who sets a session filter in fixed London time will be one hour off during the two short gap periods, even though the filter is correct for the rest of the year.
Which time zone should your bar data use?
Store and filter bars in the exchange's own time zone, which is America/Chicago for CME futures, unless your software converts daylight saving time correctly for every date. The time zone of a data file is the clock its timestamps are written in. Providers use exchange time, Eastern Time, UTC or the user's local time, and the file often does not say which.
Hypothetical example
A trader tests an ES rule that trades only the stock session. The data is stored in UTC. The trader sets the session filter to 14:30–21:00 UTC, which is correct in January. In July, 14:30 UTC is 9:30 a.m. CDT. The filter now skips the first hour of the stock session and adds the 3:00 to 4:00 p.m. CT hour, when only futures trade. The rule makes most of its trades in the first hour. For roughly two-thirds of the year, the months of daylight saving time, the filter misses most of the rule's trades, and the test does not show it.
Run these checks before the first backtest:
- Find the data's time zone. In ES data, a large volume jump should appear at the start of the 8:30 a.m. CT bar. Note the clock time at which it appears in your file. If the file header says only "CST", trust the volume jump, not the label.
- Check both seasons. Repeat the check on a January date and a July date. If the volume jump moves by one hour in your file, the timestamps are in a zone that does not follow US daylight saving time, such as UTC or Taiwan time.
- Check the change weeks. Look at the Monday after the second Sunday in March and the Monday after the first Sunday in November. Missing or duplicated hours there point to a conversion error.
- Check the daily break and the Sunday open. ES data should have no bars from 4:00 p.m. to 5:00 p.m. CT, and the first bar of the week should start at 5:00 p.m. CT on Sunday. Bars inside the break mean the timestamps are shifted.
- Check how bars are stamped. Some programs label a bar with its start time, others with its end time. A bar marked "9:00" can mean 8:00 to 9:00 or 9:00 to 10:00. A one-bar shift can let a rule use a price before it existed, a leak described in the guide to look-ahead bias in backtests.
The article on backtest data quality covers other data problems, such as gaps, bad ticks and contract rolls.
What does this mean for testing a strategy?
The time zone is part of the strategy, because a filter written on the wrong clock trades different hours in summer and in winter. Write the session down in Central Time before you test. For example: "Trade ES from 8:30 a.m. to 3:00 p.m. CT, flat by 2:55 p.m. CT, no trades on early-close days." Then confirm with the checks above that your data's timestamps match that sentence on a January date and a July date. A rule written like that sentence can be entered as entry and exit conditions in the strategy generation of AlphaPrime (Valynox), with the flat-by time in the afternoon as one of the exits.
In AlphaPrime, trading sessions are part of the backtesting settings, together with data resolution, next-bar execution, fees and slippage, so every candidate in a search is tested on the same hours.
What this means if you use AlphaPrime: confirm the time zone of your own historical bar data first, then set the trading session in Central Time terms, so the hours you research are the hours you would trade.
Frequently asked questions
What time does the stock market open in Central Time?
The NYSE and Nasdaq regular session opens at 8:30 a.m. Central Time, Monday to Friday. This is 9:30 a.m. Eastern Time. Pre-market trading can start earlier, from 3:00 a.m. CT at the widest, depending on your broker.
Are stock market hours different in CST and CDT?
No. The hours are 8:30 a.m. to 3:00 p.m. Chicago time in both winter (CST) and summer (CDT). Only the offset from UTC changes, from UTC−6 in winter to UTC−5 in summer. Times in UTC or in zones without US daylight saving time, such as Taiwan, move by one hour.
Is CST the same as China Standard Time?
No, but both use the abbreviation CST. Central Standard Time is UTC−6 and China Standard Time is UTC+8, a 14-hour difference. When a data file or chart is labelled only "CST", check a known event, such as the 8:30 a.m. CT open, to find out which one it means.
When does the US stock market open in Taiwan time?
The regular session opens at 22:30 Taiwan time in US winter and at 21:30 in US summer. It closes at 05:00 or 04:00 the next morning in Taiwan. The change follows the US daylight saving dates, the second Sunday in March and the first Sunday in November.
What time is the early close in Central Time?
On NYSE early-close days, the stock market closes at 1:00 p.m. ET, which is noon CT. The day after Thanksgiving is a common example. Futures may follow their own holiday schedule, so check the exchange calendar for both markets.