When Does the US Stock Trading Week Start and End Under 23/5?

Under the 23/5 schedule, the US stock trading week starts on Sunday at 9 p.m. ET with an overnight session and ends on Friday at 8 p.m. ET, with a one-hour pause every weekday evening. Nasdaq and NYSE Arca are scheduled to start this schedule on December 6, 2026, subject to the readiness of the consolidated data feeds and remaining exchange rule filings. Holidays shift the start: there is no session on the evening before an exchange holiday, and trading resumes at 9 p.m. on the evening of the holiday itself, or on Sunday if the holiday is a Friday.

When does the trading week start under 23/5?

The first session of the week opens at 9:00 p.m. ET on Sunday. The SEC order approving Nasdaq's 23/5 rules, dated April 10, 2026, keeps the market closed during weekend hours "except that the trading week will commence with a Night Session on Sunday nights at 9:00 PM ET." NYSE-listed stocks trade overnight on NYSE Arca, and the NYSE extended-hours FAQ (version 4.0, August 2026) gives the same Sunday-through-Thursday 9:00 p.m. start for its Overnight Session. The weekly calendar is one piece of a broader change, explained in hi2morrow's overview of what changes when US stocks trade 23 hours a day.

The Sunday session belongs to Monday. The CTA Extended Trading Hours FAQ, updated September 29, 2026, treats each window from 9:00 p.m. to 8:00 p.m. the next evening as one trading day, so Sunday night is simply the opening stretch of Monday's trading day. That is also why the Sunday start comes with a condition: CTA opens the Sunday session only if Monday is a business day, and Nasdaq defines its Night Session as running into a next calendar day that is a business day.

For traders outside the US, the Sunday open falls on Monday morning in most of Asia. While New York is on standard time, 9:00 p.m. ET is 2:00 a.m. UTC on Monday, which is 6:00 a.m. in Dubai and 10:00 a.m. in Singapore. US daylight saving time begins on March 14, 2027, and from then until November the Sunday open moves to 1:00 a.m. UTC. The first live Sunday session is planned for December 6, 2026; from November 8 to December 5, CTA runs the new schedule in production with test symbols only.

When does the trading week end?

The week ends at 8:00 p.m. ET on Friday, when the Day Session that began at 4:00 a.m. closes. Nasdaq's approval order says the trading week "will end at the conclusion of the Day Session on Friday," and there is no Friday-night or Saturday session on either exchange. The next opportunity to trade on an exchange is 9:00 p.m. on Sunday, a gap of 49 hours.

Friday's trading day is also the longest stretch of continuous exchange trading in the week, running 23 hours from 9:00 p.m. on Thursday to 8:00 p.m. on Friday. Trades executed on Thursday night carry Friday's trade date, which affects when sale proceeds settle; hi2morrow's article on which trade date a 10 PM overnight stock trade gets works through those dates.

Not every venue moves to the new week. According to the Nasdaq global trading hours FAQ, Nasdaq Texas keeps its 7 a.m.–7 p.m. schedule, Nasdaq PSX keeps 8 a.m.–5 p.m., and Nasdaq's options exchanges keep their current hours. The NYSE FAQ says the other NYSE Group equities exchanges also stay on their existing schedules. The 23-hour week applies to Nasdaq and NYSE Arca and to the consolidated tape that carries their quotes and trades.

How do holidays change the overnight session?

A holiday removes the session that would have started the evening before it. Nasdaq's rule says that when the exchange is closed for a holiday, the closure takes effect at 8:00 p.m. ET on the prior calendar day, and the market reopens at 9:00 p.m. on the holiday itself, unless the holiday is a Friday, in which case trading resumes on Sunday at 9:00 p.m. CTA's FAQ states the same rule from the data side: no session starts on the evening before a US holiday, none runs during regular hours on the holiday, and the next one begins on the holiday evening if the following day is a business day.

The exchanges give concrete examples. Nasdaq's FAQ explains that if Monday is an exchange holiday, trading begins at 9:00 p.m. on Monday and runs until 8:00 p.m. on Tuesday. For NYSE Arca, the FAQ describes a New Year's Day that falls on a Thursday: the Late Session runs until 8:00 p.m. on Wednesday, December 31, and trading resumes with the Overnight Session at 9:00 p.m. on Thursday, January 1. In both cases the holiday evening is not a holiday session; it is the opening stretch of the next trading day.

The holiday list is defined in the rules. Nasdaq treats as non-business days New Year's Day, Martin Luther King Jr. Day, Presidents' Day, Good Friday, Memorial Day, Juneteenth, Independence Day, Labor Day, Thanksgiving, and Christmas when they fall on a weekday. Columbus Day and Veterans Day are not on that list, so under Nasdaq's definition the overnight session runs as usual before them, even though banks close and stock trades do not settle on those days.

A Monday holiday stretches the weekend. Trading stops at 8:00 p.m. on Friday and does not resume until 9:00 p.m. on Monday, a gap of 73 hours instead of the usual 49. On Martin Luther King Jr. Day, January 18, 2027, and Presidents' Day, February 15, 2027, there is no Sunday-night session at all.

What changes on early-close days?

On an early-close day, the regular session ends at 1:00 p.m. ET, and the evening session ends early too. NYSE's holidays and trading hours page says the late trading sessions of NYSE Arca and the other NYSE Group equities exchanges close at 5:00 p.m. on those days, and CTA's FAQ moves its end of day to 5:01 p.m. Nasdaq's rule ends the trading day at 8:00 p.m. "or such earlier time as may be designated" when it closes early.

What happens next depends on the calendar. Nasdaq's rule says that after an early close it resumes trading at 9:00 p.m. on the same day, unless that day is a Friday, in which case it waits until Sunday. In practice, the published early closes do not trigger that same-evening restart. In NYSE's calendars for 2026 through 2028, every early close is either a Friday after Thanksgiving or the day before a holiday: Thursday, December 24, 2026; Friday, November 26, 2027; Monday, July 3, 2028; and Friday, November 24, 2028. On each of those evenings, the Friday or holiday rule applies, and no exchange overnight session starts.

The July 2028 case shows how the rules combine. Monday, July 3 closes at 1:00 p.m., Arca's late session ends at 5:00 p.m., nothing trades on Monday night because Tuesday is Independence Day, and the overnight session opens at 9:00 p.m. on Tuesday, July 4. The NYSE FAQ gives the same pattern for a Thursday July 4, with Wednesday's late session ending at 5:00 p.m.

What does the first holiday season under 23/5 look like?

Thanksgiving 2026, on November 26, falls before the planned launch, so the first holidays under the new week are Christmas and New Year's Day. Both fall on Fridays. Thursday, December 24, 2026 is an early-close day: the regular session ends at 1:00 p.m., NYSE Arca's late session at 5:00 p.m., and the CTA FAQ confirms there is no session on Thursday night. Christmas Day is closed, nothing trades over the weekend, and the next session opens at 9:00 p.m. on Sunday, December 27. New Year's week repeats the pattern without the early close: Thursday, December 31 is a full trading day until 8:00 p.m., and the next session starts at 9:00 p.m. on Sunday, January 3, 2027.

Consider a trader who holds 300 shares of ABC, which closes at $40.00 at 1:00 p.m. on December 24 and trades at $39.80 in the late session. A sell limit at $39.50 entered through a broker at 6:00 p.m. that Thursday has no exchange session to reach until 9:00 p.m. on Sunday, 76 hours later, compared with 49 hours on an ordinary weekend. If the order fills at the Sunday open, the 300 shares bring $11,850 (300 × $39.50), and the trade carries a Monday, December 28 trade date. If news over the long weekend sends the first overnight prints to $37.00, the order simply rests above the market, and the position is worth $750 less than at the limit before any trade happens.

The rest of the 2027 calendar follows the same rules. Good Friday, March 26, 2027, removes Thursday night's session and the weekend gap runs from 8:00 p.m. Thursday to 9:00 p.m. Sunday. Juneteenth is observed on Friday, June 18, and Christmas on Friday, December 24, 2027, so each produces the same Thursday-to-Sunday gap. Thanksgiving 2027 shows the mid-week case described in the CTA FAQ: there is no session on Wednesday, November 24, the session for the early-close Friday begins at 9:00 p.m. on Thanksgiving evening, and the week ends at 5:00 p.m. on Friday, November 26 for NYSE Arca. hi2morrow's calendar of US stock market holidays, early closes, and settlement dates lists every 2026 and 2027 date with its settlement effect.

Do broker overnight sessions follow the same week?

Not necessarily. The exchange calendar describes when Nasdaq and NYSE Arca will trade, but brokers that already run their own overnight products set their own hours. Interactive Brokers' overnight trading page, for example, says that for sessions starting on days the NYSE is closed, its ATS accepts orders from 5:30 p.m. ET and executes from 6:00 p.m. That is three hours earlier than the exchange restart on a holiday evening, and it is the broker's policy, not an exchange rule.

As of October 2026, neither the exchange documents nor broker pages say whether broker-run sessions will be realigned with the exchange week after December 6. Before a long weekend, check which session your order is eligible for, which venue it will be routed to, and whether your broker holds, cancels, or resubmits it between Friday evening and Sunday night.

Alexander Styopin's professional view: the new schedule removes most overnight gaps but makes the remaining ones easier to forget. A trader used to reacting at 3 a.m. on a Wednesday can be caught by a 76-hour Christmas gap or a 73-hour Monday-holiday weekend, both well beyond the ordinary 49-hour weekend. Mark those gaps in your calendar at the start of each quarter, size positions for them the way you would for an earnings release, and do not assume that the Sunday-night open will offer the liquidity of a regular session.

Educational material only. Not investment or legal advice. Session hours, holiday schedules, order handling, and settlement rules can vary by exchange, broker, account type, and jurisdiction, and the launch schedule described here may change.

Author: Alexander Styopin, hi2morrow analyst and economist with 25 years of experience in the US stock market