Arnold & Porter Discusses SEC Approval of Nasdaq Proposal to Expand Trading Hours

Key Takeaways

• SEC greenlights Nasdaq's 23‑hour, five‑day trading schedule.
• Day Session runs 4 AM‑8 PM ET; Night Session 9 PM‑4 AM ET.
• Night Session limited to limit orders, with extra risk disclosures.
• Existing listing, market‑maker and enforcement rules stay unchanged.
• Nasdaq must file additional rule change before Night Session launch.

Pulse Analysis

The SEC’s approval reflects a broader market shift toward continuous trading, driven by global investors seeking access to U.S. equities outside traditional hours. As digital‑asset exchanges already operate around the clock, Nasdaq’s 23‑hour schedule narrows the convenience gap, potentially drawing volume from after‑hours venues and boosting overall market depth. Regulators also see the move as a way to modernize the National Market System, aligning it with the expectations of algorithmic and high‑frequency traders who thrive on extended liquidity.

Operationally, Nasdaq will split the day into two distinct sessions. The Day Session merges the former pre‑market, regular and post‑market periods, preserving existing order‑type rules and market‑maker obligations. The newly created Night Session, however, will be more restrictive: only limit orders are permitted, and participants must acknowledge heightened risk disclosures. A one‑hour nightly pause (8 PM‑9 PM ET) will handle system maintenance and corporate‑action processing, ensuring data integrity before the next trading window opens. These structural tweaks aim to balance expanded access with safeguards against volatility spikes and operational failures.

For market participants, the extended hours promise greater flexibility and the chance to capture price movements driven by foreign news cycles or macro‑economic releases that occur outside U.S. business hours. Liquidity providers may adjust incentive programs to compensate for thinner night‑time volumes, while brokers will need to update client disclosures and trading platforms. In the longer term, the 23‑hour model could set a new industry standard, prompting other exchanges to seek similar extensions and reshaping the competitive landscape of global equity trading.