US stock exchanges to trade 23 hours a day from December

US stock exchanges are significantly extending their trading hours. From 6 December, investors will be able to trade 23 hours a day, five days a week on Nasdaq and NYSE Arca, among others. The regular session from 9:30 a.m. to 4 p.m. will remain in place, but a much longer trading period will surround it. The move is part of a broader shift towards round-the-clock trading on financial markets.

In brief:

• Nasdaq and NYSE Arca will start trading 23 hours a day on 6 December.
• The trading week will run from Sunday evening to Friday evening, with one hour of maintenance each day.
• Thin liquidity outside regular hours can lead to wider spreads and greater price fluctuations.

Trading week runs from Sunday to Friday evening

The extended trading week begins on Sunday evening and continues until Friday evening. Each day there is a one-hour interruption for system maintenance. The regular session, from 9:30 a.m. to 4 p.m. US time, remains unchanged alongside the extended hours.

The US markets regulator SEC is working on the necessary infrastructure to make this 23/5 model possible. According to reports, a further expansion to 24/7 trading is among the possibilities for a later phase.

Brokers decide which clients get access

Not every investor automatically gets access to the extended trading hours. Brokers themselves decide which securities can be traded outside the regular session and which clients may use these services.

Outside peak hours, liquidity is generally lower, which can lead to larger spreads between bid and ask prices and greater price fluctuations. That makes trading outside the regular session risky, especially for retail investors.

The NYSE has long been exploring the possibilities for extended trading. Earlier, the exchange already examined 24/7 stock trading via blockchain, and the SEC recently approved a temporary exemption for trading in tokenised shares. The step towards 23/5 is therefore part of a broader trend in which traditional financial markets are pushing their boundaries.