Nasdaq and NYSE move to 23-hour trading on 6 December: what algo traders need to check

Nasdaq and NYSE Arca plan to add an overnight session for US stocks and ETFs on Sunday 6 December 2026, running from 9pm to 4am ET and taking US stock trading to nearly 24-hour (23 hours a day, five days a week). Both launches still depend on outstanding approvals and on the consolidated data feeds being ready, so treat the date as a target until the first session opens.

What happened

The SEC approved Nasdaq's proposal to extend trading hours on 10 April 2026, and NYSE Arca filed its amended rule on 12 May 2026, according to Jones Day (September 2026). WilmerHale (29 September 2026) reports that the SEC has conditionally approved 23x5 trading on five exchanges (24X, Cboe EDGX, MEMX, Nasdaq and NYSE Arca), with the approvals tied to the consolidated data feeds (the SIPs) going live on 6 December.

On the NYSE side, only NYSE Arca is extending its hours. NYSE's extended-hours FAQ (August 2026) says the other NYSE Group equities exchanges will keep their current hours, and that the Arca launch is subject to SEC approvals, SIP availability and DTCC's modernisation work. As of 21 October 2026, several rules needed for the framework still required SEC approval, with more technical and fee filings expected before December.

The details that matter

The headline is "23 hours", but the rules inside the new session matter more to an automated strategy:

• Hours. The overnight session runs 9pm to 4am ET, Sunday to Thursday nights. There is a one-hour pause from 8pm to 9pm ET, Monday to Thursday, and the trading week runs from Sunday 9pm to Friday 8pm ET (Skadden, via the Harvard Law School Forum, 21 October 2026).
• Limit orders only. Nasdaq's Night Session will accept only limit orders, and unpriced orders such as market orders will not be permitted. All five approved exchanges plan to accept only orders with a limit price (WilmerHale).
• No opening auction. NYSE Arca's overnight session starts with continuous trading at 9pm, accepts orders from 8:59pm, and its first auction is still the 4am Early Open Auction. Core session hours (9:30am to 4pm) and the 4pm closing auction are unchanged.
• Orders don't carry over. Orders do not carry across session boundaries on either exchange.
• Price bands and halts. Static overnight price bands sit 20% from reference prices, and a stock halted overnight does not reopen during the overnight session (WilmerHale).
• Trade dates. Trades between 9pm and midnight ET carry the next calendar day's trade date (NYSE FAQ).
• Access through brokers. Only US broker-dealers that are exchange members can trade the session directly. Everyone else goes through a member broker, and brokers can block certain client orders overnight with firm-level controls.

Liquidity is the open question. WilmerHale (29 September 2026) cites SEC staff data showing overnight volume at about 0.9% of total NMS share volume on an average trade date as of August 2026, up 359% year on year, and the exchanges' own risk disclosures point to lower liquidity, higher volatility and wider spreads.

What it means for systematic traders

Nothing changes for a strategy that only trades 9:30am to 4pm and uses the official open and close. The risk is in strategies where time is implicit:

• A strategy with no session filter, or one that runs on a 24-hour chart, may start taking entries between 9pm and 4am if your data feed starts printing those bars.
• Indicators that reset each session, such as VWAP or the day's high and low, may reset at a different time.
• A weekday breakdown built from trade dates will put a Tuesday 10pm trade on Wednesday.
• Gap strategies assume nothing tradeable happens between the close and the open. More of that move may now happen through real overnight trades.
• Backtests have no exchange history for this session. Older overnight data comes from alternative trading systems, a different venue with its own liquidity.
• Code that sends market orders, or relies on stops that become market orders, will not behave the same overnight.

What to do before 6 December

• Check your broker's announcement and API documentation for overnight hours, which order types it accepts, and how it handles stops at night.
• Make the overnight session an explicit on/off input in your strategy, and leave it off until you've tested it.
• Confirm where your platform's session starts and where your indicators reset.
• Use the time of entry, in one time zone, when you break results down by day.
• Once the session is live, split overnight trades from day trades and judge them on their own, with realistic spread costs.

Read more

Our guide to 23-hour stock trading for algo strategies covers the backtesting and broker questions in more depth, with a Pine Script switch for the overnight session. The Pine Script session and time filter guide shows how to write time rules that survive daylight saving, and how to analyse a TradingView backtest by session, weekday and hour shows how to split results once overnight trades appear. To see how your strategy already performs by session and hour, the free Entry Analysis report works with trades from a supported broker, a platform export or any spreadsheet.