The US stock market is open six and a half hours a day, five days a week, minus holidays. Do the arithmetic and it comes to roughly 1,650 hours a year, out of 8,760. Call it 19 percent. For the other 81 percent of the year, the most liquid stock market on earth is a locked door.
The world does not pause to match. Earnings drop after the close on purpose. Politics happens on weekends. Asia trades while America sleeps. This guide walks through how the industry has papered over the mismatch, and what a genuinely always-open market changes.
The official hours, and the unofficial ones
Regular session: 9:30am to 4pm Eastern. Around it sit pre-market from as early as 4am and after-hours to 8pm, where trading is legal but thin. Spreads widen, orders are usually limit-only, and one moderate order can move a price in ways it never would at noon.
Then came overnight trading. Robinhood, Webull and Moomoo now route selected stocks through overnight venues, covering roughly Sunday evening to Friday evening. Call it 24/5. It is real progress with one hard edge: everything still stops for the weekend. Friday 8pm arrives and the door locks for two days, exactly when 48 hours of news is about to pile up.
Gaps: where closed hours send the risk
A closed market does not stop prices from changing. It stops you from trading while they change. The change arrives all at once at the next open, as a gap, and gaps are where the pain concentrates.
Hold a stock through its earnings report and you know this feeling. Micron reports after the close. Netflix can gap double digits before regular hours resume. Whatever the stock does in reaction, you watch it happen and act after. The memory sector adds a second variant: its biggest players report and trade in Seoul, so the US names gap on news that broke while the Nasdaq slept.
None of this is the market being unfair. It is the mechanical consequence of hours. Risk does not take nights off, so a market that does simply transfers the risk to whoever is holding when the music stops.
What 24/7 actually changes
Crypto settled the question of whether continuous markets can work. Bitcoin has traded every second of every day for over fifteen years, through every crisis, without an opening bell. The infrastructure lesson carried over: Hyperliquid runs perpetual futures markets continuously, and Based builds stock trading on top of it.
In a 24/7 market there is no gap, because there is no close for a gap to form across. Earnings reactions are tradable as they happen. Weekend news is tradable on the weekend. The Sunday night dread of waiting for futures to open stops being a thing. You still take losses when you are wrong. You just take them with your hands on the wheel.
Fairness is the quieter half. Exchange hours are a subsidy to people whose job is trading between 9:30 and 4 in New York's time zone. A continuous market treats a trader in Singapore, a nurse on night shift and a fund manager identically. The market is open when you are, whoever you are.
The honest fine print
Liquidity is not uniform around the clock. A Sunday 4am order book is thinner than a Tuesday afternoon one, everywhere, on every venue. Size positions accordingly.
And what trades 24/7 through Based are perpetual futures on Hyperliquid tracking stock prices, not the shares themselves. That is what makes the hours possible: contracts on an always-on decentralised platform rather than shares in a system that sleeps. Price exposure without ownership, with liquidation risk and funding fees as part of the deal; the perps guide explains both. If that trade-off fits, any market on the list is open right now, whenever right now happens to be.