Company disclosure timing and the 23-hour trading day

After-hours earnings release timing decides which trade can first reflect the news. In Eaton, Shkilko and Werner's first-quarter 2024 sample, over 90% of earnings announcements came outside the regular session, between 4:00 and 9:30 a.m. or between 4:00 and 8:00 p.m. [36]. For after-hours announcements, Berkman and Truong found the volume and price response one trading day after the date recorded in Compustat or I/B/E/S [30]. NYSE rules bar material news after the close until the earlier of 4:05 p.m. or publication of the official closing price [25], and Nasdaq asks for ten minutes' notice of certain material news released from 7:00 a.m. to 8:00 p.m. [24].

The news moves on several clocks: a wire release, a website or social post, an EDGAR filing and a notice to the listing exchange. The SEC approved Nasdaq's 23-hour, five-day schedule on 10 April 2026, with a Night Session from 9:00 p.m. to 4:00 a.m. [1]. Nasdaq targets Sunday 6 December 2026 for the start, subject to SIP readiness and any applicable SEC rule changes [20]. All times are U.S. Eastern.

Disclosure channels and Regulation FD

When an issuer shares material nonpublic information with market professionals or holders likely to trade, Regulation FD requires public disclosure at the same time if the disclosure was intentional and promptly if it was not [11]. "Promptly" means as soon as reasonably practicable, and no later than 24 hours or the start of the next day's trading on the New York Stock Exchange, whichever is later [12]. Public disclosure means a Form 8-K or another method "reasonably designed to provide broad, non-exclusionary distribution of the information to the public" [12]. The SEC named press releases through a widely circulated news or wire service as acceptable [13].

Websites, social media and Regulation FD

A website counts when it is a recognized channel, the posting reaches the market in general and investors have had a reasonable waiting period to react, which the SEC calls "a facts and circumstances determination" [14].

In 2013 the SEC applied the same test to social media [15]. Netflix's chief executive posted a streaming milestone on his personal Facebook page just before 11:00 a.m. on 3 July 2012, without an 8-K or a release through the usual channels [15]. The news reached the market incrementally, through a technology-focused blog about an hour later and a handful of outlets within two hours [15]. The SEC called it critical that companies tell the market which channels they intend to use [15]. Nasdaq's listing guide now lists websites and social media channels among the methods that comply with Regulation FD [24].

A post has a post time. When it became public is a judgment. Records need the source's time and their own capture time, as set out in datasets that state their limits.

EDGAR's 5:30 p.m. cutoff and the filing date

EDGAR runs from 6:00 a.m. to 10:00 p.m. on weekdays other than federal holidays [17]. Under Regulation S-T Rule 13, a filing whose transmission starts at or before 5:30 p.m. is filed that business day, and one that starts later is filed the next business day [10]. Most late submissions get a filing date of 6:00 a.m. the next business day, and EDGAR does not disseminate them until that day [17].

An earnings 8-K carries the release as an exhibit, and its general deadline is four business days after the event, so the filing can trail the wire [16].

EDGAR acceptance time vs filing date

In EDGAR's dissemination stream, a control block records the "Acceptance Time" to the second, described as "Time (EST)", and the submission header carries the official filing date [18]. Two 2026 filings show the gap.

Sources: [26, 27, 28].

EDGAR's JSON timestamps often disagree with the index page. In our check of 24 daylight-time 8-K and 8-K/A filings from 12 companies on 24 October 2026, the JSON's acceptanceDateTime, marked "Z" for UTC, ran 8 hours after the index page's Accepted time in 19 and 4 hours after in 5. PepsiCo's, for example, reads 2026-10-08T01:57:44.000Z against 17:57:44 on 7 October [26, 29]. The two offsets cannot both be right, so check each value against the index page.

Nasdaq MarketWatch notice and NYSE's 4:05 p.m. rule

In the Night Session, Nasdaq halts a stock when its primary listing market does [1], and a stock halted for regulatory reasons overnight does not reopen before 4:00 a.m. [5].

After-hours earnings releases and overnight trading

Timing studies differ on bad news. deHaan, Shevlin and Thornock found results consistent with bad news coming after market hours, on busy days and with less notice [31]. Michaely, Rubin and Vedrashko found negative news tends to come during trading hours, where the immediate reaction is about 50% smaller [32].

After-hours price discovery is "significant, albeit inefficient" in Barclay and Hendershott [33], and shows a large degree of informational efficiency for S&P 500 stocks from 2004 to 2008 in Jiang, Likitapiwat and McInish [34].

On post-close announcement days in the first quarter of 2024, Eaton, Shkilko and Werner found 0.14% of volume between 8:00 p.m. and midnight and 0.10% between midnight and 4:00 a.m., against 1.76% from 4:00 to 8:00 p.m. [36]. The median weighted price contribution was 70.14% from 4:00 to 8:00 p.m., against -1.04% and 0.00% in the two overnight windows [36]. In August 2026, months before the Night Session's target start, trading from 8:00 p.m. to 4:00 a.m. carried 0.9% of NMS share volume on an average trade date [9, 20].

Nasdaq's 23-hour trading day and the Night Session

The Night Session cannot start until the consolidated data plans can disseminate its quotes and trades, and Nasdaq must first file a further rule change [1]. The SIP amendments take effect once the plans' Operating Committee finds market conditions ready, including DTCC clearing [2]. On 23 October 2026, Nasdaq wrote that the regulatory proposals "proceed through the approval process" [22].

NYSE Arca plans its Overnight Session for the same date, subject to SEC approvals, SIP availability and DTCC changes [23]. The NYSE does not intend 23-hour trading "at this time" [7].

Mapping a disclosure to its first tradable price

At the daily level the usual rule holds. A release after 4:00 p.m. shows up in the next day's close-to-close return, the pattern Berkman and Truong found [30]. The 23-hour schedule leaves that in place, because the closing cross stays at 4:00 p.m. [1]. Extended-hours trades carry ".T" and do not set the daily high, low or last sale [2]. Intraday work changes more.

Overnight price bands end at 4:00 a.m. "to accommodate the well-established practice of issuers releasing earnings announcements ... during pre-market hours" [5]. The event-study methods note sets out windows and baselines.

Two questions remain. Commissioner Peirce, speaking for herself, asked whether EDGAR must change for the overnight session [37]. The second is how Regulation FD's outer limit, which refers to the start of NYSE trading [12], reads once Nasdaq trades overnight while the NYSE has no 23-hour plan [7].

Rillor's public communications and market response data holds selected public statements as issued, with their timestamps, entities and classifications, each paired with price observations in a declared window and random-baseline controls.

Read the full report

The full report adds the rule text behind each clock, the venue approvals and their conditions, the studies with their samples, the EDGAR timestamp check and the complete list of 39 sources.