A futures contract trades almost around the clock, but the day it trades in is not one continuous thing. It has a settlement, a maintenance halt, a reopen, and a cash session with its own open and close. Each edge changes who is in the market and how much size is on the book, and a chart that ignores them draws levels through hours that were never the same market.
The clock, for the equity index contracts
- The week opens on Sunday at 5:00 p.m. Central time and runs to Friday at 4:00 p.m. Central.
- Every weekday trading halts from 4:00 p.m. to 5:00 p.m. Central for maintenance. The 5:00 p.m. reopen starts the next trade date.
- The cash session for US stocks runs 9:30 a.m. to 4:00 p.m. Eastern. The futures trade through it, but the depth, the speed and the participants change at both ends.
- Daily settlement for the E-mini S&P 500 is set from the volume-weighted average price of trades in the thirty seconds ending at 3:15 p.m. Central.
Other contracts keep other hours. The exchange publishes each product's schedule and its settlement procedure, and those pages are the source when the question matters.
Why settlement is a level
Settlement is the price every open position is marked to at the end of the trade date. Margin calls, profit and loss statements and many funds' daily reports are calculated from it. Because so much accounting hangs on that one number, the market has a reason to remember it: a return to yesterday's settlement is a return to the price where every holder is flat on the day.
Why the overnight session is thinner
Between the cash close and the next cash open, most of the natural hedging flow from stocks is absent, because the stocks are not trading. What remains is futures-only business: global macro desks, overnight risk being adjusted, and market makers quoting smaller size at wider spreads. Volume per hour is a fraction of the day's, so a given order moves price further. A level built overnight is built on less participation than one built at 10:00 a.m.
What the edges do to a chart
A session template decides which hours a chart shows and where its daily bar begins. Change the template and yesterday's high, low and open all move, because they are computed over a different set of hours. Two traders looking at the same contract with different templates will disagree about where the day's range is, and both charts are correct for the hours they were told to use.
What to actually do with it
- Know which session your chart's daily bar is built from, and keep it the same on every chart you compare.
- Mark settlement as its own level rather than trusting the close of a bar that may end at a different minute.
- Give overnight highs and lows the weight of the volume that made them, and treat the cash open as the moment the real size arrives.