How US Equities Actually Trade: Sessions, Gaps, and What Most Data Providers Miss

The stock market is not open from 9:30 AM to 4:00 PM. That is one session out of four. US equity trading activity spans a full 24-hour cycle, fragmented across different venues, participant bases, and liquidity regimes. Any system consuming equity price data that only covers regular trading hours is blind to more than 16 hours of price discovery per day.

This is the first entry in Know Your Feed, a series breaking down how price data actually works across every major asset class. Starting with the most complex: US equities.

Four Sessions, Four Different Markets

Unlike crypto, which trades 24/7 on a relatively unified set of venues, US equity trading is split into four distinct sessions within each 24-hour cycle. Each session operates with different participants, different liquidity profiles, and often different price behavior.

Overnight (Sun-Thu, 8:00 PM to 4:00 AM ET) is currently dominated by Blue Ocean ATS, an SEC-registered Alternative Trading System. This session opens the trading week on Sunday evening and handles over $1B in average nightly volume.

Pre-market (Mon-Fri, 4:00 AM to 9:30 AM ET) is driven by institutional flows and early reactions to overnight news. Liquidity builds significantly after 8:00 AM when economic data releases begin. Only limit orders are accepted.

Regular trading hours (Mon-Fri, 9:30 AM to 4:00 PM ET) is the primary session on NYSE and NASDAQ. This is where the highest liquidity, tightest spreads, and full designated market maker participation occur. LULD (Limit Up-Limit Down) circuit breakers are active during this window.

Post-market (Mon-Fri, 4:00 PM to 8:00 PM ET) sees heavier retail participation via broker platforms. Earnings releases are commonly issued in this window, making it a high-volatility period with wider spreads than regular hours.

The implications for anyone consuming equity price data are significant. A price feed that only covers regular hours will miss overnight reactions to geopolitical events, pre-market institutional positioning, and post-market earnings gaps. For DeFi protocols using equity feeds for mark-to-market, funding rates, or liquidations, this gap in coverage is a structural risk.

The Single-Venue Problem

US equity trading is fragmented across 16 registered exchanges, numerous dark pools, and alternative trading systems. The SIP (Securities Information Processor) consolidates quotes from all these venues into the NBBO, the best bid and offer available across the entire market.

Not all venues contribute equally to price discovery.

Some market data providers, especially those targeting crypto and DeFi use cases, source equity prices from a single low-volume venue attracted by simpler licensing terms. The problem is significant: these venues handle a fraction of total US equity spot volume. Spreads are meaningfully wider than on primary exchanges like NASDAQ and NYSE, where the majority of price discovery occurs.

A price from a single low-volume venue is that venue's price. It is not "the stock price."

For any system using equity prices for collateral valuation, funding rate calculation, or liquidation triggers, the source venue matters. A price that deviates from the primary exchange can trigger false liquidations or create arbitrage opportunities against the protocol's users. The cheaper the licensing, the further the price may sit from where real volume trades.

Why Prices Gap Between Sessions

A price gap occurs when a stock opens at a significantly different price than the previous session's close. Because each session has different liquidity profiles and participant bases, price information does not flow smoothly across boundaries. These gaps are a structural feature of equity markets, not anomalies.

The most common catalysts include earnings releases (often announced in post-market), geopolitical or macro events (which can move prices sharply in overnight or pre-market sessions), analyst upgrades and downgrades (which set the tone before regular hours open), and the weekend itself. The 64+ hour window between Friday at 8:00 PM and Sunday at 8:00 PM is the largest information accumulation period in the weekly cycle. The overnight session on Sunday provides the first price signal after that void.

LULD circuit breaker halts also create intra-session gaps. When a stock moves too fast during regular hours, trading is paused. Upon resumption, price can jump in either direction.

For DeFi protocols, these gaps represent a distinct category of risk. Lending protocols valuing equity collateral may face instant under-collateralization after an earnings gap. Perpetual futures platforms need to handle session boundaries where the feed transitions from one data source to another. Stop-loss logic that works in continuous crypto markets does not protect against the discontinuous pricing inherent in equities.

How Pyth Approaches Equity Data Differently

The Pyth Network's equity feeds are built on a fundamentally different architecture than most data providers in the crypto ecosystem. Three design choices define the approach.

First-party institutional publishers. Pyth's US equity feeds receive data from a curated subset of institutional data providers, including market makers, exchanges, and trading firms with direct market access across all sessions. These are the institutions that participate in price discovery, not intermediaries repackaging someone else's data.

Primary-venue benchmarking. Publisher accuracy is measured against the mid-point price at the primary market for each stock. The 99th percentile deviation from this benchmark must remain within 20 basis points. This ensures the aggregate price reflects where real, high-volume price discovery occurs, not where licensing is simplest.

Session-specific publisher curation. Because different publishers participate in different sessions, Pyth maintains separate feed configurations for each trading window. Each feed requires a minimum of five active publishers, selected based on price freshness (95%+ of prices delivered fresh within each trading day) and accuracy against the primary-venue benchmark.

24/5 Coverage Through Blue Ocean ATS

Through an exclusive data partnership, Pyth is the only blockchain-based oracle provider publishing overnight US equity trading data from Blue Ocean ATS. This addresses the most significant gap in modern equity data infrastructure: the overnight session.

Blue Ocean ATS is an SEC-registered Alternative Trading System with FINRA oversight. It covers US National Market System (NMS) stocks from Sunday through Thursday, 8:00 PM to 4:00 AM ET. The pricing is executable and ATS-sourced, meaning it reflects actual trades on a regulated venue, not indicative quotes or AMM-derived estimates.

Other data providers either go dark during the overnight window or attempt to fill the gap with indicative pricing and modeled estimates. Pyth publishes prices from actual trades on a regulated ATS. That distinction matters for any system where pricing accuracy has financial consequences.

Combined with pre-market, regular, and post-market coverage, this gives Pyth the only true 24/5 US equity data feed available to DeFi and institutional consumers.

Pyth Pro: The Enterprise Layer

Pyth Pro delivers this multi-session equity data through standard APIs (WebSocket, REST, FIX) designed for institutional integration. Key capabilities for equity consumers include on-demand pricing (subscribers pull prices when needed), customizable payloads with fields including price, bestBid, bestAsk, confidence, and marketSession, and cryptographic verification for onchain settlement across EVM, Solana, and other formats.

The marketSession field is particularly important for equity consumers. It tells protocols exactly which trading session the price originates from, enabling session-aware risk logic. A price tagged "overnight" carries inherently different liquidity characteristics than one tagged "regular." Protocols can apply different collateral haircuts, margin requirements, or staleness thresholds based on this field.

What This Means for Builders

Engineers and protocol designers building products that reference equity prices need to internalize a few structural realities.

Equity prices are not continuous. They vary by session, venue, and liquidity regime. A feed that treats all prices as equivalent regardless of session context will produce unreliable risk calculations.

Session boundaries create real discontinuities. Pausing new activity for a few seconds around transitions (for example, 3:59 to 4:01 PM ET) can prevent impact from price jumps between feeds.

Confidence intervals matter more for equities than for crypto. Spread and liquidity vary dramatically across sessions. Using the lower bound of the confidence interval for collateral valuation and the upper bound for outstanding loan positions is one approach to managing this variance.

Gap risk from earnings and macro events bypasses traditional risk controls. Tightening collateral requirements ahead of known earnings dates, freezing liquidations during LULD halts, and requiring higher margin for positions held through weekends are all practices that address this structural risk.

The Bigger Picture

US equities are the most regulated, most liquid, and most structurally complex asset class to price correctly. Getting equity data right is the hardest test a price feed provider can face.

Pyth's approach to equities, sourcing from the institutions that actively trade them, benchmarking against primary venues, and covering all four sessions, demonstrates the depth of infrastructure required to serve institutional-grade data consumers.

This is the first in a series. FX, commodities, and fixed income each have their own structural complexities, their own challenges that most data providers handle poorly or ignore entirely. Each edition of Know Your Feed will break them down.

For the full technical reference, including feed IDs, integration formulas, and the complete publisher network breakdown, the US Equities Asset Info Pack is available as a downloadable resource.

Pyth Pro delivers 3,000+ price feeds across equities, crypto, FX, commodities, and fixed income through a single integration. That includes 24/5 US equity coverage across all four trading sessions, sourced from the institutions that set prices. Book a demo with an authorized distributor here.

Disclaimer

This post is for informational and educational purposes only and does not constitute legal, financial, investment, or any other form of professional advice. The discussion of NBBO, SIPs, and related regulatory concepts is provided for general context and should not be relied upon as a complete or authoritative statement of applicable law or market structure. All accuracy figures and performance comparisons cited herein are based on empirical analysis conducted during specific historical observation periods. These figures reflect historical observations only and are not a guarantee or promise of future performance or data quality; actual results may vary materially depending on market conditions, liquidity, and other factors. References to specific exchanges, venues, protocols, or products are for illustrative purposes and do not constitute an endorsement or warranty of any kind. Digital assets, decentralized finance protocols, and related products carry significant risks, including the risk of total loss. Readers should conduct their own independent due diligence and consult qualified professionals before making any decisions based on the information presented here.