U.S. stock exchanges expand trading hours as 23-hour market launch nears

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US stock exchanges 23-hour trading

Highlights

Nasdaq, NYSE Arca, and three other U.S. exchanges will introduce 23/5 trading, opening Sundays 9pm EST and closing Fridays 8pm EST, with daily one-hour pauses.
The formalized extended hours target international demand, particularly from Korean retail investors, aiming to shift liquidity from alternative venues like Blue Ocean to major exchanges.
Analysts warn of increased manipulation risks and thin liquidity during overnight sessions, with institutional investors cautious due to high spreads and operational concerns outside normal U.S. trading hours.

Launch plan and trading structure

As reported by Financial Times, the new regime is expected to start across five exchanges, including Nasdaq and NYSE Arca, and will run on a 23/5 schedule rather than true 24-hour trading.

Trading is set to begin at 9pm Eastern Standard Time on Sundays and continue until 8pm EST on Fridays, with a mandatory one-hour pause from 8pm to 9pm EST from Monday to Thursday. The planned extension formalises longer access that some brokers, including Robinhood and Charles Schwab, already provide, while bringing more activity onto official exchanges rather than alternative venues.

Support for the move also reflects international demand, especially from Korean retail investors seeking easier access to U.S. technology shares. Alternative Trading Systems such as Blue Ocean already offer extended trading, but these platforms typically have lower liquidity, less oversight and wider bid-ask spreads than established exchanges.

Liquidity and oversight risks for investors

Critics say thinner liquidity during U.S. overnight hours could make the market more vulnerable to manipulation and poor execution, particularly for retail investors trading when participation is limited.

James Angel of Georgetown University says the Securities and Exchange Commission is reacting to broader market pressures rather than leading the change, including competition from crypto markets and tokenised assets that trade continuously. A former enforcement official warns that overnight conditions create a favourable setting for manipulation, while cross-border activity can make abusive trading harder to police.

Institutional investors may initially stay cautious, with Jeff O'Connor of Liquidnet saying market depth and spreads still make overnight trading expensive. He adds that stronger volumes could eventually draw traditional money managers seeking to capture returns from overnight price movements, but concerns remain over operational resilience, including the risk of data outages or social media-driven volatility outside normal business hours.

In our earlier coverage of AI financing stress hitting U.S. stocks and bonds, we explained how hotter inflation revived rate-hike fears and triggered a selloff led by technology shares. We also noted that widening credit spreads were pressuring AI-linked companies’ funding models, with high-profile issuers seeing bond prices fall and yields jump as investors reassessed risk.

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