Dealer Gamma Vanna Charm Flows
Overnight CME Globex ES & Cboe GTH Gamma Hedging Gaps Into 09:30 ET Open
Explore overnight options microstructure between 16:15 ET and 09:30 ET: thin CME Globex ES depth, Cboe Global Trading Hours (GTH) SPX quoting, and why overnight gaps trigger 09:30 ET RTH catch-up flows.
A startling empirical stylized fact documented by Federal Reserve Bank of New York researchers shapes every institutional overnight volatility book: virtually 100% of net cumulative S&P 500 returns over multiple decades occurred between the 16:00 ET close and the 09:30 ET open, whereas cumulative intraday Regular Trading Hours (RTH) returns hovered near flat with higher volatility! Why does overnight microstructure behave so differently from RTH, and how do options dealers manage gamma across CME Globex ES futures and Cboe Global Trading Hours (GTH)?
Within the 0DTE Index Options, Dealer Gamma Pinning, Vanna & Charm Rehedging silo and our 0DTE Dealer Gamma, Vanna & Charm Flows Guide, dissecting the 17.5-hour overnight bridge reveals hidden execution alpha at both 08:30 ET and 09:30 ET.
Discrete Overnight Gap P&L and Pre-RTH Catch-Up Hedging Equations#
Suppose at 16:00 ET (tclose) aggregate dealers hold net gamma Γnet hedged to zero delta, and overnight macro news in Tokyo or Frankfurt moves CME Globex ES by ΔSON = S{09:30} − S{16:00}. Because resting limit-order depth on Globex at 02:30 ET is 75% to 88% thinner than during RTH (raising execution impact cost cON ≈ 3.5 × cRTH), automated dealer hedging splits into two distinct cohorts—24-hour global market makers who hedge continuously on Globex/GTH (αGTH ≈ 55% of inventory) versus RTH-centric desks who widen discrete bands until 08:30–09:35 ET (1 − α_GTH ≈ 45%):
Quantitative Pricing Model: Overnight CME Globex ES & Cboe GTH Gamma Hedging Gaps#
- Discrete Unhedged Overnight Gap Slippage: ΔPnLgap = 1⁄2 · Γdealer · (ΔSON)2 − ΘON · Δt_ON (hurts short-gamma dealers severely on >1.2% overnight gaps!).
- 08:30 ET Macro Pre-Open Catalyst: Because CPI, PCE, Retail Sales, and NFP release at 08:30:00 ET, 100% of Vanna & Gamma rehedging occurs in CME ES + Cboe GTH BEFORE cash equities open!
- Worked Morning Gap-Fade Calculation (Overnight ES Rallies +38 Pts from 5,850 to 5,888 on Benign European Data, Net Dealer GEX = +$5.4B / 1% = +$92.3M/pt, α_GTH = 0.55):
- Global desks sold −$1.93B ES overnight; RTH-anchored desks release remaining −$1.58B (−5,365 ES contracts!) between 09:25 ET and 09:50 ET—explaining the classic 15-pt post-open gap fade!
Traders verify ES-to-SPX overnight fair-value basis using our Futures Fair Value Calculator and calibrate 09:30 ET opening ranges in the 0DTE Expected Move Calculator.
24-Hour Global SPX / ES Dealer Gamma Hedging Clock#
Comparing Overnight Liquidity Windows for Index Volatility Desks#
| Global Time Window (ET) | Active Venues & Counterparties | CME ES Book Depth & SPX Spreads | Dominant Hedging Behavior |
|---|---|---|---|
| 16:15 – 18:00 ET (AH Tech Earnings) | CME Globex ES/NQ (GTH paused 17:00–20:15) | Moderate depth; no listed SPX option trading during 17:00–20:15 ET maintenance | Pure futures delta hedging on NVDA/MSFT/AAPL earnings |
| 20:15 – 02:59 ET (Tokyo / BoJ) | Cboe GTH + CME Globex via Apex Futures | Thin ES book; GTH SPX bid-ask ~2.5x RTH width | Only large BoJ/China shocks cross Whalley-Wilmott bands |
| 03:00 – 08:29 ET (London / ECB) | European desks (House of Borse, iDealing) | Depth builds to ~40% RTH; active GTH SPXW 0DTE positioning | European macro funds pre-position 0DTE straddles |
| 08:30 – 09:30 ET (US Data → Cash Open) | Full US institutional desks + FCMs | Deep ES liquidity; Vanna fires at 08:30 ET sharp | Delayed RTH gamma catch-up completes by 09:50 ET |
09:30–10:30 ET Overnight Gap Fate by Gap Size & Dealer GEX#
Institutional macro accounts regulated across CFTC, NFA, and ESMA jurisdictions increasingly execute 0DTE SPX event straddles during Cboe GTH at 08:25 ET—capturing the exact 08:30 ET CPI jump without holding 16 hours of overnight theta from the prior afternoon!
Frequently asked questions
Can institutional traders trade SPX and VIX options at 03:00 AM ET during the London open?
Yes! Cboe Global Trading Hours (GTH) operates nearly 24x5 (from 20:15 ET Sunday/weekday evening right through 09:25 ET morning) for SPX, SPXW (including upcoming 0DTE!), XSP, and VIX options, allowing European and Asian macro desks to hedge live before U.S. cash opens.
Why do morning gaps often get faded in the first 45 minutes of RTH when Net Dealer GEX is positive?
Many systematic option funds and secondary market makers suppress automated Globex hedging overnight to avoid wide spreads, leaving pent-up stabilizing hedges unexecuted. Between 09:30 ET and 10:00 ET when RTH liquidity peaks, executing those delayed +GEX hedges pushes SPX back toward prior close!
What happens at 08:30 ET—one hour BEFORE the NYSE cash equity open—on CPI and NFP days?
U.S. Bureau of Labor Statistics CPI and Nonfarm Payrolls drop at 08:30:00 ET while cash equities are still closed! CME Globex ES and Cboe GTH SPX options absorb 100% of the initial spot jump and Vanna vol crush 60 full minutes before NYSE opening bells ring!
How should overnight variance weight be separated from RTH variance weight in 1-DTE pricing?
Historically, the 17.5-hour overnight close-to-open window accounts for roughly 28% to 35% of total 24-hour S&P 500 variance on normal days, surging above 60% when Nvidia earnings (16:20 ET), BoJ decisions, or 08:30 ET CPI prints fall inside that overnight span.
Publication record
- Published
- November 13, 2026
- Updated
- November 14, 2026
- Author
- Dr. Alistair Finch, CQF, FRM
- Review
- Review not recorded
- Automated fact check
- Passed in the stored pipeline record
- Source URLs
- 3 recorded
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Dr. Alistair Finch, CQF, FRM. (2026, November 14). Overnight CME Globex ES & Cboe GTH Gamma Hedging Gaps Into 09:30 ET Open. VolSurface Desk. https://volsurfacedesk.com/desk-notes/overnight-globex-es-session-gamma-hedging-gapsRelated Dealer Gamma Vanna Charm Flows & Institutional Briefings
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