JPMorgan Chase kicked off the 2026 earnings season on Tuesday, January 13, reporting its fourth-quarter results before the market opened, the same slot the bank has used every January for years. Two days later, Netflix, Microsoft, and Nvidia would report in the opposite window, after the closing bell, once the regular session had already gone quiet. That split is not random. It follows a pattern tied to what each company does, how the SEC regulates disclosure, and, according to one of the more surprising findings in financial research, it does not actually work the way most investors assume.

Options traders heading into recent reporting seasons have priced in average swings of 4.7% to 7.4% on S&P 500 stocks around their earnings releases, using data compiled by Bloomberg and Goldman Sachs. Whether that swing happens in the calm of after-hours trading or in the chaos of the opening bell depends entirely on a scheduling decision companies make months in advance, one built around SEC deadlines, banking tradition, and a piece of academic research that most retail investors have never heard of.

What BMO and AMC Actually Mean

BMO, before market open, generally covers releases between 6:00 and 9:00 a.m. Eastern, timed to land before NYSE and NASDAQ open for regular trading at 9:30 a.m. AMC, after market close, covers releases roughly between 4:00 and 5:30 p.m. Eastern, once the 4:00 p.m. closing bell has already rung. A handful of companies report in the middle of the trading day, but that is rare enough to be treated as an outlier rather than a real third category.

The distinction matters because it decides which session absorbs the first shock. A BMO report gets digested in the roughly three hours of pre-market trading before the opening bell, so the stock often gaps at 9:30 already reflecting the news. An AMC report has no equivalent built-in cushion during the regular session, so the first reaction plays out in thinner after-hours volume, with the fuller verdict often not arriving until the following morning’s open.

Why Banks Almost Always Report Before the Bell

Banks kick off nearly every earnings season, and they do it before the opening bell almost without exception. JPMorgan’s January 13, 2026 report came before the market opened, followed the next day by Bank of America, Wells Fargo, and Citigroup, and the day after that by Goldman Sachs, Morgan Stanley, and BlackRock, a cascade that repeats every quarter with only minor date shifts. Part of the reason is structural: bank accounting cycles close faster than those of manufacturing or technology companies, since most of their assets are marked to market or based on standardized loan and trading metrics rather than complex inventory or revenue-recognition judgment calls.

Part of it is also tradition and signal value. A strong JPMorgan report sets an optimistic tone that can lift the broader financial sector before markets even open for the day, while a weak one can trigger defensive positioning before the bell. Reporting before the open, rather than burying the news in an illiquid after-hours session, lets that signal ripple through the entire day’s trading rather than getting compressed into a thin overnight window. Economic data released around the same 8:30 a.m. window follows a similar logic: give the market a full session to absorb news that could move the entire sector.

Why Big Tech Almost Always Reports After the Close

Large technology and growth companies overwhelmingly choose the opposite window. Nvidia’s fiscal fourth-quarter 2024 report, released February 21, 2024, for the fiscal year that ended January 28, 2024, is a representative example: the company posted adjusted earnings per share of $5.16 on revenue of $22.1 billion, well above the Bloomberg-surveyed consensus of $4.60 on $20.4 billion, and released the numbers after the close, sending the stock up 7% in after-hours trading rather than mid-session on the NYSE floor or NASDAQ order book.

The practical reason is disruption management. A single company the size of Apple, Microsoft, or Nvidia moving 5% to 15% in the middle of a live trading session can distort volume, trigger algorithmic trading cascades in correlated names, and complicate order execution for anyone holding a position elsewhere in the market. Reporting after the close pushes that volatility into after-hours trading, a lower-volume, lower-liquidity session that absorbs large price swings without disrupting the broader market’s regular-hours pricing.

The SEC Deadline Nobody Talks About

Behind every BMO or AMC decision sits a regulatory clock most investors never see. Large accelerated filers, companies with a public float of $700 million or more, must file their quarterly Form 10-Q within 40 days of the fiscal quarter’s end, a deadline that became permanent under SEC rules finalized in December 2005, when regulators scrapped a planned further acceleration to 35 days. The same filers must submit their annual Form 10-K within 60 days of fiscal year-end, a separate deadline phased in for fiscal years ending on or after December 15, 2006, as part of the broader post-Enron push for faster disclosure that began in 2002.

The deadline does not dictate morning versus evening, but it does compress hundreds of companies into overlapping windows, which is part of why the reporting order tends to follow a consistent sequence: banks first, since their books close fastest, then industrials, then large-cap technology, and finally retailers, whose fiscal calendars often run a few weeks behind because their quarters are defined around holiday shopping cycles rather than the calendar quarter.

Regulation FD Quietly Pushed Earnings Later

Reporting timing was not always this rigid. The SEC adopted Regulation FD, for fair disclosure, in August 2000, effective that October, banning companies from privately briefing analysts on earnings figures before releasing them to the general public. Academic research published in the Journal of Applied Business Research in 2011 found a measurable, lasting effect from that rule: annual earnings announcement times shifted significantly later after Regulation FD took hold, for both companies that had previously announced during trading hours and those that had already reported after the close.

The logic tracks the regulation’s intent. Before Reg FD, companies could quietly walk analysts through results before the official release, which meant the timing of the public announcement mattered less since the information had already partially leaked into prices. Once simultaneous public disclosure became mandatory, companies gained a stronger incentive to release everything into the least disruptive window available, after the close, where the first wave of institutional reaction happens in a contained after-hours session rather than live in front of every retail order flying into the regular market.

The Volatility Study That Contradicts the Conventional Wisdom

The popular assumption is that after-hours releases are the “safer” choice, giving the market a quiet overnight window to absorb news before regular trading resumes. A study led by Northwestern University professor Matt Lyle, examining roughly 70,000 quarterly earnings announcements with precise timestamps from 2006 to 2014, found close to the opposite. Announcements made before the market opened were associated with greater stock price volatility than those made after the close, and that elevated volatility persisted for a full five trading days following the announcement, not just the first session.

The researchers also found that pre-open announcements took roughly four full days to reach the same level of price stability that post-close announcements achieved almost immediately. Their working theory was timing relative to normal life: investors on the West Coast and those with jobs are more likely to be at their desks and able to react quickly to a 4 p.m. Eastern release than to one dropped before sunrise, so post-close news gets processed faster and more completely, while pre-open news lingers and gets reassessed over a longer stretch. Understanding when volatility peaks during the trading day adds useful context here, since the slower-digesting BMO reports often collide with the first-hour volatility spike that already exists at every market open regardless of news.

How Earnings Season Actually Unfolds Across a Quarter

The sequence is consistent enough that traders build entire calendars around it. Banks open the season in the first one to two weeks, typically the second week of January, April, July, and October. Industrials and transportation names, companies like RTX, UPS, and General Motors, follow roughly two weeks later. Large-cap technology clusters in the final week of the bank-industrial window and the first two weeks after, historically landing in the final days of January and the first week of February for Q4 results. Retailers close out the season weeks later, since companies like Walmart and Target run fiscal quarters tied to holiday shopping rather than the calendar quarter.

That sequencing has real informational value beyond curiosity. Weak bank results can signal tightening credit conditions before industrial or tech names even report, and disappointing consumer-facing retail results at the tail end of the season often color the market’s read on the broader economy heading into the next quarter. A rough opening week from the banks does not guarantee a rough season overall, but it consistently shapes the tone investors bring into the market’s first hour for weeks afterward.

What the Timing Choice Actually Protects Against

The disruption that BMO and AMC timing is designed to manage is not hypothetical. Extreme single-stock volatility during a live session can interact with market-wide circuit breakers, the automatic trading halts triggered by sharp index-wide moves, since a handful of mega-cap names now represent an outsized share of S&P 500 weighting. A single company the size of Nvidia or Apple swinging double digits mid-session has real potential to nudge broader indexes toward those thresholds, which is a structural risk that simply does not exist in the same way once trading has already moved into the lower-volume after-hours or pre-market sessions.

That risk management, more than habit or convenience, is the throughline connecting a decades-old SEC filing deadline, a 2000 fair-disclosure rule, and a 2011 academic finding that overturned what most traders assumed about which window was actually calmer. The BMO-versus-AMC choice looks like a scheduling footnote on an earnings calendar. In practice, it is one of the few genuine levers a company has over how its most volatile day of the quarter actually plays out.