The open, the close and everything outside regular hours

Most of the trading day is a steady stream of separate trades. The open and the close work differently, and so do the hours before and after them. Knowing how helps you read some of the largest prints you will see.

The regular session

U.S. stocks trade in a regular session from 9:30 a.m. to 4:00 p.m. Eastern on trading days. Most trading happens then. The market is closed on weekends and on a short list of holidays. On a few days each year, it closes early, usually at 1:00 p.m. Eastern.

The session begins and ends with an auction. Between them, trades happen one at a time as orders meet.

How the opening and closing auctions work

An auction collects orders for a while and then matches them all at once, at one price. The exchange where a stock is listed runs the auction and picks the price at which the most shares can trade. Every matched order trades at that price, at the same moment.

The opening auction sets the official opening price on the listing exchange, using orders gathered before 9:30 a.m. The closing auction sets the official closing price, which is usually the price quoted as the day's close. On early-close days, the closing auction happens at the early close.

The close draws a lot of trading. Many funds value their holdings at the closing price, so they aim their trading at the close. Orders for the closing auction can be entered well before 4:00 p.m., and they all trade together when it runs. Because the matched shares are reported together, one Close Auction print can be very large. It can rank among a ticker's largest trades since 2016. Because that volume is scheduled, its size is less unusual than the same size in the middle of the session.

BigTape marks auction prints with a rounded square, sized by rank like any other print. They are labeled Open Auction or Close Auction. On the chart, the shaded extended-hours blocks end at the opening bell and start again at the closing bell, so auction squares sit right at those boundaries.

Many orders in one print

An auction print combines many orders, large and small, matched at one price. A $1 billion Close Auction print tells you how much traded at the close. It does not tell you that any single participant traded that much.

The same holds for its rank. A Close Auction print that ranks #2 since 2016 is the second-largest single print in that ticker's history. That is a fact about how the auction was reported, and it says nothing about who took part.

BigTape ranks an auction print the same way as any other print, by dollar value against the ticker's history since 2016. The square shape is there so you can tell at a glance that a large print came from an auction.

Extended Hours

Trading also happens before 9:30 a.m. and after 4:00 p.m. Eastern. The hours available depend on the venue and on your broker. BigTape labels any trade outside the regular session as Extended Hours. The chart shades those hours, so you can see where the regular session begins and ends. Extended Hours prints are ranked like any other print, and the shading keeps them easy to tell apart.

Fewer people trade outside regular hours. Prices can move further between trades, and one trade can be large compared with the volume around it. Many companies publish their results before the open or after the close, so a stock can trade actively outside regular hours on those days.

Two more labels help with prints at unusual times. A Ghost Print is a trade priced outside that day's regular-session high and low. That high and low come from regular hours only. A Ghost Print's price usually reflects how the trade was arranged, not where the market was. Late Report marks a trade published late and out of order, so its time is when it was reported, not necessarily when it happened. Ghost Prints stay one click away, in the Everything layers or by their own switch.