The End of the Closing Bell: Rethinking Institutional Trading in a 23/5 Cycle

For decades, the structure of global capital markets has been tied to a predictable rhythm. Exchanges opened, liquidity concentrated within regional sessions, and markets closed at the end of each day. This cadence shaped the investment industry’s entire operating model.

The movement toward a 23/5 trading environment represents a structural change to that long-standing rhythm. Several major exchanges and market operators are pursuing extended trading sessions that would effectively keep equity markets open for roughly 23 hours each weekday, from Sunday evening through Friday evening, with only a brief technical interruption each day.

Exchanges Push Toward 24-Hour Markets

Modern capital markets have always been global in participation but regional in structure. Liquidity moved sequentially from Asia to Europe to North America, as each region’s exchanges opened and closed. While electronic trading expanded access to after-hours sessions, meaningful liquidity typically concentrated during local market hours.

This regional sequencing created predictable operating windows. After the close of a primary market, firms had time to complete trade-capture validation, reconcile positions, process corporate actions, calculate performance, and produce accounting records. Even firms with global footprints relied on these pauses. The existence of a daily close made it possible to run batch processing cycles, resolve breaks, and generate official books before the next trading session began. And these pauses supported system resilience by providing natural maintenance windows.

But in late 2025, Nasdaq made headlines by filing for U.S. Securities and Exchange (SEC) approval to extend stock trading to 23 hours per day, Monday through Friday. The proposal outlines a new overnight “Night Session” from 9 p.m. to 4 a.m. ET, on top of existing pre-market and regular hours, with a one-hour daily break (8–9 p.m. ET) for maintenance and to reset the trading day.

If the SEC signs off, Nasdaq could launch this nearly 24-hour schedule in late 2026. Nasdaq says it will wait to ensure market infrastructure (like data feeds and clearing systems) can fully support trading in the middle of the night before officially opening the floodgates.

And the push for nonstop trading isn’t limited to Nasdaq. In 2025, Cboe Global Markets announced plans in 2025 to expand one of its exchanges (EDGX) to a 24/5 trading week to cater to increasing demand from overseas investors, especially in Asian time zones. And in a significant milestone, a startup exchange, 24X, launched in October 2025 as the first SEC-approved U.S. stock exchange with a 23/5 mandate.

NYSE has been a bit more cautious. In early 2025, NYSE (through its all-electronic NYSE Arca platform) received SEC approval to lengthen its trading day from 16 hours to 22 hours. That means adding an overnight session but keeping a two-hour nightly shutdown. Why stop short of 24 hours?

NYSE’s reasoning is that “everyone needs a break” ─ not just people, but also the market’s plumbing. Clearinghouses like DTCC/NSCC don’t yet operate 24/7, so trades executed at 3 a.m. wouldn’t immediately clear and settle. Until post-trade processes catch up, NYSE prefers a daily timeout to process corporate actions and ensure the market remains orderly.

By proposing 22-hour trading as a first phase, NYSE aims to meet demand for more access “without introducing unnecessary risk [or] complexity.” If industry coordination (such as upgrading data feeds that aggregate prices) goes smoothly, NYSE could implement its extended hours later in 2026, eventually moving to a full 23/5 schedule when the support systems are ready.

Opportunities and Concerns for Institutional Investors

For asset managers and asset owners, the prospect of 23/5 trading presents a mix of potential benefits and serious questions. On the upside, near-continuous trading could improve global access and price discovery. Investors wouldn’t have to wait until the next day’s opening bell to see market-moving news or overseas developments reflected in stock prices. A portfolio manager in London or Singapore could reallocate U.S. holdings during their own business hours, rather than transacting in off-hours or using alternative instruments. In theory, that means fewer overnight surprises. Geopolitical event at 2 a.m.? Instead of waiting, 23/5 market traders could react immediately, potentially smoothing out some price shocks.

However, many institutions are approaching 23/5 trading with caution. One major concern is liquidity. Will enough buyers and sellers show up at 3 a.m. to make fair and efficient markets? Critics argue that simply stretching the hours could lead to painfully thin trading and more volatile price swings in the dead of night.

If volumes remain low in the wee hours, large asset managers worry they could face wider bid-ask spreads and higher trading costs for big orders. And if markets truly never sleep, would investment firms need to staff their trading desks 24/5?

Even some veteran traders wonder if the industry will need to create “a whole new ecosphere” of overnight portfolio managers and support teams to monitor markets and respond to events at all hours. That implies higher operational costs and potential burnout concerns, burdens that smaller asset managers or trading firms may struggle with.

The Elimination of the Daily Reset

Investment operations, accounting, data management, and technology architectures have historically depended on the existence of a daily market close. As that boundary erodes, firms must rethink how positions are maintained, books of record are defined, and control frameworks operate when there is no longer a clean end-of-day reset.

There are several areas that need to be considered:

• Implications for Investment Operations - The move to continuous markets requires a corresponding evolution in operating models. Investment operations organizations must transition from batch-processing mindsets to event-driven workflows. Instead of developing solutions to mitigate daily cycles, teams must monitor processes continuously and intervene when exceptions arise. Traders will need greater awareness of corporate actions impacting trade execution, and EMS/OMS integration with corporate action systems will become even more important.

• Data and Technology Architecture Considerations - Continuous markets place significant demands on data infrastructure. Firms must move toward unified data models that represent transactions, positions, and reference data consistently across the enterprise. Streaming and event-driven architectures become critical, and cloud-native platforms provide the elasticity needed to handle variable processing loads across time zones.

NAV Production, Client Reporting, and Regulatory Implications - Net asset value (NAV) calculations and client reporting processes are deeply tied to valuation cut-off times. Continuous trading makes determining the appropriate valuation point more complex and increases demand for intraday transparency. Firms must establish governance policies that define when positions are considered official for reporting purposes.

Conclusion

The move toward 23/5 trading marks a structural inflection point in market infrastructure. As trading becomes nearly continuous, the traditional reliance on batch cycles and separate books of record becomes increasingly fragile. Unified, continuously updated books of record supported by modern platforms enable real-time risk management, intraday transparency, and more resilient control frameworks.

For many asset managers, maintaining effective coverage across extended hours introduces cost, staffing, and technology challenges that many are not currently structured to absorb. Firms must be willing to explore not just tactical solutions, but possibly new ways to operate that help to control cost and complexity.

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