U.S. stocks are set to enter a 23-hour trading era starting December 6, with Nasdaq and NYSE Arca among four major exchanges adding overnight sessions. According to Sina Finance, the expansion is aimed at competing with round-the-clock trading in cryptocurrencies and prediction markets, while also capturing incremental demand from overseas investors.

The SEC said overnight trading currently accounts for about 1% of total U.S. stock turnover, but its year-on-year growth has reached 358%. The article said the U.S. stock market will keep only one hour of closure each day, from 8 p.m. to 9 p.m., for system maintenance and trade processing.

Institutional investors remain cautious, with liquidity and bid-ask spreads seen as the main concerns. Crisil Coalition Greenwich senior analyst David Easthope said the key issue is market quality in extended hours, not simply operations or staffing. Joseph Saluzzi, co-head of equity trading at Themis Trading, said he has little interest in the new rule, while Jeff O'Connor, head of market structure at Liquidnet, said institutions are in a wait-and-see mode.

The SEC said overseas investors accounted for 37% of overnight trading volume in the second quarter this year. The article also said that in August, just 15 stocks made up 50% of overnight volume, compared with 256 stocks needed to reach the same share during regular trading hours.

Blue Ocean Technologies CEO Brian Hyndman said existing active participants will transition smoothly once the December rule takes effect. He added that the continued absence of buy-side institutions and investment banks means the market still lacks a key piece of the puzzle.

The DTCC switched to a 24x5 model in June, running from 8 p.m. New York time on Sunday to 8 p.m. on Friday. The Securities Information Processors have also been approved to extend operating hours.