A 2018 working paper by Matthew Lyle of the Kellogg School of Management and three co-authors found that about 96 percent of the U.S. companies they studied released quarterly earnings outside regular trading hours between 2006 and 2015, with 48 percent of those releases landing before the open and 52 percent after the close.
That near-even split looks like habit, yet the two slots produce measurably different results for price stability and for media attention.
The evening slot is also changing character, as U.S. exchanges prepare overnight sessions that would make the hours after the close a nearly continuous market.
What follows is the evidence behind the choice, from exchange notice rules to four decades of academic work, ending with a timing table by release type.
Pre-open or post-close: what the data shows
Price stability favors the evening
The Lyle paper, built on 85,875 firm-quarters of timestamped announcements, found that pre-open announcers showed about 28 percent more cumulative abnormal volatility over the second to fifth trading days after the release than post-close announcers.
Abnormal trading volume over those same days ran about 6 percent higher for the pre-open group.
Processing time is the authors' explanation, since a 7:00 a.m. release leaves investors two and a half hours before the opening bell while a 4:10 p.m. release leaves them the whole evening.
Intermediaries moved more slowly as well: after a pre-open release, a smaller share of analyst revisions and news stories came on the first trading day and a larger share over the next four days than after a post-close release.
Coverage favors the morning
Attention runs the other way.
A Journal of Accounting and Economics study by Ed deHaan and two co-authors, drawing on more than 120,000 timestamped earnings announcements, found that releases after trading hours drew 7 percent fewer news articles and 19 percent fewer EDGAR downloads after controlling for firm characteristics and the news itself.
On the busiest reporting days, news articles fell 12 percent, which makes a crowded date a coverage problem in its own right.
Taken together, the research describes a trade-off rather than a single right answer.
Post-close releases buy steadier price discovery at the cost of some coverage, while pre-open releases buy coverage at the cost of a longer and noisier adjustment.
Thin liquidity outside the core session
In a 2003 Review of Financial Studies paper, Michael Barclay and Terrence Hendershott reported that only 4 percent of Nasdaq trading volume took place after hours, outside the 9:30 a.m. to 4:00 p.m. regular session.
Volatility fell far less than volume did.
Among the 250 most active Nasdaq stocks from March to December 2000, the first half hour after the close carried 20 percent of the volume of the session's final half hour but 54 percent of its volatility.
Before the open the imbalance was sharper, with the last pre-market half hour showing 5 percent of the opening half hour's volume and 72 percent of its volatility.
Once the bell rang, volume drained quickly, falling 80 percent between 4:00 and 4:30 p.m. and a further 85 percent between 4:30 and 5:00 p.m.
The authors concluded that after-hours trading produces significant but inefficient price discovery, with individual trades carrying more information and prices carrying more noise.
Their sample dates from 2000, but one mechanism still matters for issuers: post-close trades caused temporary price changes that were later reversed.
For a company choosing a slot, the practical reading is to give investors the most time to read before the regular session sets the price.
The exchange rules that set your earliest safe minute
NYSE
NYSE's 2026 compliance guidance for listed companies requires a call to its Market Watch group at least 10 minutes before material news is released between 7:00 a.m. ET and the 4:00 p.m. close.
Dividend and stock distribution announcements need that 10-minute notice at any hour, including outside trading hours.
Halts are where a timing error becomes public.
From 9:25 a.m. to 4:00 p.m., NYSE's practice is to halt a stock pending dissemination if it believes the news is material and the company has not followed the notice policy.
Between 7:00 a.m. and 9:25 a.m., NYSE imposes a news-pending halt only at the company's request.
After the bell, Section 202.06 of the Listed Company Manual bars material news until 4:05 p.m. ET or the publication of the official closing price, whichever comes first.
That restriction is meant to avoid confusion when prices on other markets after 4:00 p.m. diverge from an NYSE closing auction price that can be set after 4:00 p.m.
The notice policy also covers material news disclosed verbally on an investor call or at a conference, even when the event itself complies with Regulation FD.
Nasdaq
Nasdaq's window is wider, because IM-5250-1 requires a listed company to notify Nasdaq at least ten minutes before releasing material information between 7:00 a.m. and 8:00 p.m. ET.
When the release falls outside those hours, notice to Nasdaq's MarketWatch department is due before 6:50 a.m. ET.
Notice goes through Nasdaq's electronic disclosure system except in emergencies, and repeated failures can bring a public reprimand letter or, in extreme cases, a delisting determination.
Deals add a second clock, since an acquirer and a target listed on different exchanges each answer to their own venue's rule.
For the drafting side of the same risk, see our guide to avoiding disclosure violations in an earnings release.
Fridays, and Friday evenings in particular
Stefano DellaVigna and Joshua Pollet, studying earnings announcements from January 1995 to June 2006, found that Friday releases drew a 15 percent lower immediate price response and a 70 percent higher delayed response than releases on other weekdays.
Trading volume around Friday announcements was 8 percent lower, a result the authors, writing in the Journal of Finance in 2009, tied to limited investor attention.
Later research narrowed that picture.
The deHaan study measured no difference in market attention on Fridays, although the 7.6 percent of announcements made on Fridays carried unexpected earnings 190 percent lower than on other weekdays.
Roni Michaely and two co-authors, writing in the Journal of Accounting and Economics in 2016, located the opportunistic behavior in a single slot: Friday evening.
They found that the worst earnings news is announced on Friday evenings, followed by insider trading in the direction of the news and the largest post-earnings announcement drift.
Friday-evening announcers also released later in the evening than on other nights and were less likely to hold a conference call.
The broader pattern goes back to James Patell and Mark Wolfson in 1982, and several later studies found worse earnings news on average after the close and on Fridays.
Jeffrey Doyle and Matthew Magilke tested whether that reflects deliberate hiding by looking only at companies that switched their timing, and found no evidence that managers moved worse news into either slot.
Their 2009 paper in The Accounting Review also associated after-close announcements with greater abnormal volume, a possible sign of successful dissemination.
Berkshire Hathaway is the familiar exception, and Warren Buffett's 2017 shareholder letter, quoted at the top of the Lyle paper, gave the reason for releasing results late on Friday or early on Saturday.
That will allow you maximum time for analysis and give investment professionals the opportunity to deliver informed commentary before markets open on Monday.
Warren Buffett, 2017 letter to Berkshire Hathaway shareholders
The difference is a stated, consistent practice, whereas a one-off move to Friday evening with no call is the pattern the research associates with bad news.
After the close is turning into a live market
NYSE Arca plans to launch an overnight session from 9:00 p.m. to 4:00 a.m. ET on December 6, 2026, giving it nearly continuous trading 23 hours a day, five days a week.
That date remains subject to SEC approvals and to market data and clearing infrastructure being ready.
Nasdaq's version is already approved, as the SEC cleared its 23-hour, five-day plan on April 10, 2026, with a Night Session from 9:00 p.m. to 4:00 a.m. ET that accepts only limit orders.
Off-exchange, overnight trading already exists, and the approval order notes that it runs on alternative trading systems such as Blue Ocean.
Nasdaq told the SEC it has seen growing interest in overnight trading, particularly among investors in Asia.
Halts will carry across sessions, so if a company's primary listing market halts the stock for material news, Nasdaq's Night Session halts it too until trading resumes on that market.
Overnight prices on NYSE Arca will also sit inside static 20 percent Limit Up-Limit Down bands from 9:00 p.m. to 4:00 a.m., under an amendment to the LULD Plan described in NYSE's FAQ.
Investor-protection language has not softened either, since Nasdaq's customer disclosure rule, quoted in the approval order, warns of "an exaggerated effect from news announcements" in extended hours.
For issuers, the quiet stretch on those exchanges shrinks to a one-hour pause between 8:00 p.m. and 9:00 p.m.
Once these sessions launch, a release at 9:15 p.m. will reach a live overnight market, and if the call is not until morning, that market will price the text alone.
Two habits follow from that.
First, put complete numbers in the release itself rather than saving detail for the call, and follow our guide to formatting financial tables and charts for media pickup so the figures read cleanly on any screen.
Second, keep after-close releases early in the evening, when the Barclay and Hendershott data show after-hours volume at its deepest.
Clear the macro calendar and the newsroom clock
The Bureau of Labor Statistics publishes the Employment Situation report at 8:30 a.m. ET, and the next two releases are due October 2 and November 6.
A pre-market release timed for that minute competes with the jobs number for attention, so move it to 7:30 a.m. or earlier, or to another day.
The Federal Reserve released its September 16, 2026 FOMC statement at 2:00 p.m. ET, and afternoon news on a Fed decision day competes with that headline.
Product or contract news planned for an FOMC afternoon belongs in the morning or on a different date.
Round numbers are the next trap.
Scheduled releases tend to stack up on the hour and the half hour, and NYSE's 4:05 p.m. line makes that minute a natural default for after-close earnings.
An off-minute such as 7:50 a.m. or 4:10 p.m. keeps a headline out of the thickest stack without giving up the advantages of the slot.
Placement on outlets takes time as well.
Average distribution time at The Financial Capital is 27 minutes, so plan for placements on StreetInsider and on trading platforms such as TradingView and Stocktwits to follow your release time by about that long.
Review time belongs in the plan too, because AI review is instant but a release that needs human review can take up to five hours.
In practice, submit a 7:00 a.m. release the evening before so that a review hold cannot push it past its slot.
A timing table by release type
NYSE's guidance counts earnings and mergers among the news it generally treats as material, and the table below sets a slot for those and three other common release types, with all times Eastern.
| Release type | Preferred slot (ET) | Why | Watch for |
|---|---|---|---|
| Quarterly earnings | Monday to Thursday, 4:10 p.m. to 4:30 p.m. | Investors get the evening to process results before the regular session sets the price | NYSE's 4:05 p.m. line and the planned overnight sessions |
| Guidance cut or profit warning | Monday to Thursday, after 4:05 p.m. | Maximum processing time without the signal a Friday-evening slot sends | Full figures in the release, because overnight traders will price the text |
| Merger or acquisition | 7:00 a.m. to 8:00 a.m., with the call before 9:30 a.m. | The deal trades a full regular session with management's rationale already public | Notice rules at both listing venues and 8:30 a.m. jobs-report days |
| Capital raise | Launch after 4:05 p.m. and price before 9:30 a.m. | Bookbuilding happens while the regular session is closed | NYSE counts offerings and their pricing as material news |
| Product or contract news | 7:00 a.m. to 8:00 a.m. or mid-morning | Releases before the close drew more news coverage than after-hours releases | Exchange notice and a possible halt if the news is material |
A leak overrides every row, because Nasdaq's rule says unusual market activity can require a clear public announcement even before a matter has reached the board.
Before locking the time, run five checks.
- Compare the date with the BLS and Federal Reserve calendars and with how many other companies report that day.
- Confirm which exchange notice window applies and who will make the call or electronic submission.
- Set an off-minute, such as 4:10 p.m. rather than 4:00 or 4:05.
- Submit early enough to clear review, and if you are new to The Financial Capital, open an account well before the release date.
- Write the release so it can be priced without the call, because once overnight sessions launch, the first trade on your news may happen at night.
