On December 6, U.S. equities markets will take their biggest step yet toward an always-on market. The Nasdaq Stock Market will introduce a new session running from 9:00 p.m. to 4:00 a.m. ET, to create “23/5” trading: 23 hours of continuous markets, five days a week, with a one-hour pause each night for processing and trade-date rollover.
The move to 23/5 trading was the backdrop for the SEC Roundtable on Preparations for 24-Hour Trading in Washington, where regulators, exchanges, clearing agencies, market makers, and brokers gathered to stress-test one question above all others: Is the market actually ready?
For Chuck Mack, Senior Vice President of North American Markets at Nasdaq, as well as nearly all of his fellow panelists, the answer was a confident yes — the product of a multi-year, industrywide effort rather than a single-threaded leap.
“There are a lot of green lights,” Mack told the panel. “We are on track across both of our roles as processor of the Tape C SIP [Securities Information Processor] and as an operating exchange. [We have] a lot of confidence in the December 6 date — none of us see it as a target, we see it as the go-live.”
A Deliberate Approach
Mack was transparent that Nasdaq was careful in its approach to 23/5 trading.
“We listened to the market and to our clients, then we got very involved,” he said, citing input from the APAC region, from U.S. clients, and from infrastructure providers.
That feedback loop shaped the structure of the new trading day itself, including the 8:00–9:00 p.m. ET pause built in ahead of the overnight session. Mack credited the collaborative process behind the SIP’s national market system plans, which coordinate the consolidated tape across exchanges.
“It can be slow and challenging” to move something forward by committee, he acknowledged — but “the industry really came together in a very good way.”
Resiliency as a “Puzzle Piece”
Speaking about how firms like Nasdaq are building resiliency into their 23/5 plans, Mack stepped back to make a broader point about how the industry approaches complexity.
“We all operate — together and separately — multiple technological systems,” he said. “Across the entire industry I wouldn’t know how to count them all, and even within firms there are many interdependent systems.”
Rather than treating 23/5 as an isolated challenge, Mack argued it fits into a discipline the industry has already mastered: designing elements as pieces interacting with a broader puzzle.
“You don’t design systems without thinking about interdependencies — how you maintain the system, do failover, do software updates, and add new products and features,” he said, adding that 23/5 trading “is just another thing that you’re pulling into that complex but well-designed system across the entire industry.”
That same instinct to treat resilience as an evolving discipline carried into the panel’s discussion of cybersecurity. Asked how AI-accelerated cyber threats might change the calculus for an overnight session, Mack noted that Nasdaq already runs a wide array of systems around the clock.
“The fact that we’ll have a couple more systems running eight hours longer doesn’t significantly change the cyber policies and standards we set. We have a very robust program that constantly evolves as new technology emerges, and we account for that.”
A Good First Step, Not a Finished Product
As the industry continues to gear up for December 6, Nasdaq’s perspective continues to be clear: the move to 23/5 trading represents a deliberate, phased expansion of market access — built on proven implementation discipline, tested collaboration across the industry, and a clear-eyed view that resilience is never finished, only continuously reinforced.
Reflecting on the SEC Roundtable, Mack said, “These industry conversations provide such a valuable opportunity for collaboration and information sharing. As we approach December 6th, Nasdaq’s guiding principles are focused on transparent communication, industry cohesion, and focusing on client needs – that’s what will make this launch a success.”
