That shift was the backdrop for the SEC's Roundtable on Preparations for 24-Hour Trading in Washington, where regulators, exchanges, clearing agencies, market makers and brokers gathered to stress-test one question: is the industry actually ready?

Nasdaq SVP of North American Markets Chuck Mack: "There are a lot of green lights. We are on track across both of our roles as processor of the Tape C SIP and as an operating exchange... none of us see [December 6] as a target, we see it as the go-live."

Nasdaq's approach has been shaped by direct input from clients and infrastructure providers across the globe — including the 8:00–9:00 p.m. ET pause built into the new trading day for processing and trade-date rollover.

On resiliency, Chuck Mack framed 23/5 as one more piece of a discipline the industry already knows well: "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."

On cybersecurity: "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."