TL;DR. A 0DTE (“zero days to expiration”) option is a contract whose final trading session is its expiration day. On the S&P 500 index, you can now buy or sell a same-day call or put every weekday. As of August 2025, 0DTE contracts accounted for a record 62.4% of all SPX options volume, averaging roughly 2.4 million contracts per day, with retail traders responsible for about 53% of that activity (Cboe, Sept 2 2025). The mechanics are not new — what changed is the schedule. This piece explains exactly what a 0DTE option is, how the daily expiration calendar was built, what the Greeks do in the final hours, and where same-day trades quietly blow up.
What “0DTE” actually means
Every listed option has an expiration date. “DTE” counts the calendar days from today until that date. A standard monthly contract that expires three weeks from now is a 21‑DTE option; the moment the calendar rolls to its expiration morning, that same contract becomes a 0DTE option for the rest of its trading day. Nothing about the contract itself changes — only the time remaining.
What is new is that you can start a position that already has zero days left. Cboe lists Monday, Tuesday, Wednesday, Thursday and Friday S&P 500 (SPX) options every week. On any trading day you can buy a contract whose final tick is the close of that day. The same is true of XSP (the 1/10‑sized SPX cousin), and of the major ETF options — SPY, QQQ and IWM — whose daily expirations are listed by Cboe, NYSE Arca, Nasdaq ISE and the other U.S. options exchanges.
How the daily SPX schedule got built
Cboe launched SPX Weeklys in the early 2010s and steadily filled in the calendar. The last gaps closed in 2022. Cboe announced both additions on April 13 2022; Tuesday SPX Weeklys began trading on April 18 2022, and Thursday Weeklys followed on May 11 2022, completing the Monday–Friday schedule (Cboe Global Markets press release). From that day on, every trading session has been an SPX expiration, and the “0DTE” bucket has been a live, every‑day product rather than a once‑a‑week event.
The contract you are actually trading
It helps to look at one specific contract. SPX options use a $100 multiplier, so a single contract gives you exposure to $100 × the index. They are cash‑settled and European‑style: you cannot be assigned early, and any in‑the‑money value is paid in cash at settlement (Cboe SPX specifications). ETF options on SPY, QQQ and IWM are different: they settle into shares of the ETF and are American‑style, so they can be assigned at any time before expiration.
A worked example
Suppose SPX is trading at 6,000 at 10:00 a.m. on a Wednesday. You buy one 0DTE SPX call with a strike of 6,005 for a premium of $4.50. Because of the $100 multiplier, the cost is $4.50 × 100 = $450 per contract. Three things now determine your P&L between now and the close:
- Where SPX settles. If the index closes at 6,015, the call is worth its intrinsic value of $10.00 (6,015 − 6,005). You collect $1,000 in cash; profit is $1,000 − $450 = +$550.
- How fast time decays. Every hour you hold this contract burns through a chunk of the $4.50 you paid in time value. If SPX is still at 6,000 at the close, the call expires worthless and you lose the full $450.
- How violently the underlying moves. With only hours left, a 0.2% index swing — a routine intraday move — can be the difference between a 100% gain and a total loss.
The Greeks at zero days
If you have read our companion piece on delta, gamma, theta, vega and rho, this is where the textbook intuition starts misbehaving. As time to expiration approaches zero, three things happen at once:
- Gamma explodes around the strike. A near‑the‑money 0DTE call’s delta can swing from 0.20 to 0.80 in minutes. That is what traders mean by a “charm” or “pin” effect — the option is barely sensitive to anything except the underlying touching the strike.
- Theta becomes punishing. An at‑the‑money option loses time value on a curve that gets steeper the closer to expiry you are, because option time value is roughly proportional to the square root of time remaining. The last hour of decay is larger than the previous several hours combined.
- Vega goes to zero. Implied volatility moves stop helping or hurting an option that has no more “time” to fill with volatility. By the close, the only thing that matters is realized price vs strike.
That combination — high gamma, brutal theta, no vega — is what makes 0DTE feel different from any other options trade. The exposure is more like a binary bet on the next few hours than the slow, multi‑week trade most options textbooks describe.
Why traders use them
Same‑day options are popular for three honest reasons and at least one bad one.
- Defined‑risk intraday hedges. A portfolio manager worried about a 2 p.m. Fed statement can buy 0DTE SPX puts for a known premium and let them expire if nothing happens. The cost is predictable; an overnight hedge is not.
- Event trades. CPI prints, FOMC, jobs and major earnings days are now “0DTE days” for many funds, because the move you care about happens before the close.
- Premium selling. Selling 0DTE iron condors or credit spreads collects theta quickly. The income is real; the tail risk is also real.
- Lottery tickets. A $4.50 call that can pay $1,000 if SPX moves 0.2% the right way looks irresistible. It is also the reason most retail 0DTE accounts lose money — the expected value is roughly zero before fees, and meaningfully negative after.
A snapshot of the 0DTE market
The figures below come from Cboe’s own monthly insights posts and Q4 commentary. They show how dominant same‑day flow has become in SPX options.
| Period | 0DTE share of SPX volume | 0DTE ADV (contracts) | Notes |
|---|---|---|---|
| Full‑year 2025 | ~59% | ~2.3 million | Traders Magazine year‑end report |
| August 2025 | 62.4% | ~2.4 million | Record monthly share (Cboe) |
| Retail share of 0DTE | ~53% | — | Estimated by Cboe research |
| Daily SPX schedule completed | 100% | — | Tue 4/18/22 + Thu 5/11/22 added |
The market‑impact debate
Regulators and academics have spent the last two years arguing about whether 0DTE flow destabilizes the broader market. The fear is that dealers who sell same‑day options have to hedge their gamma exposure intraday, and that those hedges — buying as the market rises and selling as it falls — could amplify moves. Cboe’s research team has pushed back, pointing out that buying and selling 0DTE volume is roughly balanced and that the largest intraday moves of the last few years have happened on days when 0DTE flow was, if anything, quieter than usual (Cboe Insights).
The honest answer is unsettled. What is clear is that 0DTE has changed where volatility shows up. A market that used to express fear by bidding up one‑month implied volatility (the VIX) now expresses it through one‑day implied vol — a series Cboe publishes as VIX1D. That is why the headline VIX can sit at 14 while individual sessions still chop violently. We covered this dynamic in our piece on dispersion and the VIX.
The Greeks profile in pictures
The chart below shows why a 0DTE option behaves so differently from the same option a month from expiry. Theta (the daily time‑decay charge) is small until the final week, then accelerates sharply. Gamma (the rate at which delta changes) does the opposite — near zero for a back‑dated option, and enormous in the final hours for a near‑the‑money strike.
Common mistakes
- Holding through the close hoping it “comes back.” Long 0DTE options that are out‑of‑the‑money at the close are worth exactly $0. There is no overnight, no recovery, no “wait for tomorrow.”
- Confusing SPX and SPY. SPX is European‑style and cash‑settled — you cannot be assigned a stock position. SPY 0DTE is American‑style and physically settled — if your short option finishes in‑the‑money you wake up long or short SPY shares with a margin call attached.
- Ignoring pin risk on short positions. An option that settles right at the strike can be assigned or expire worthless — you find out after the close. Traders selling 0DTE credit spreads at the strike take this risk every Friday afternoon.
- Sizing as if it were a normal option. A 0DTE position with the same dollar premium as a one‑month position usually has multiples of the gamma exposure. The right comparison is to a small futures position, not to a regular options trade.
What to learn next
If 0DTE is the “extreme case” of an options position, the standard machinery still applies. Start with the building blocks: calls, puts, strike and expiry, then the Greeks, then how the market actually prices an option — the Black‑Scholes model. Once those are second nature, 0DTE stops feeling like a different product and starts looking like the same product with the clock turned all the way down.
Sources
- Cboe Global Markets Insights, “SPX 0DTE Options Jump to Record 62% Share in August” (Mandy Xu, Sept 2 2025): cboe.com
- Cboe Global Markets press release, “Cboe to Launch Tuesday and Thursday Expirations for S&P 500 Index (SPX) Options” (April 13 2022): ir.cboe.com
- Cboe SPX Options Contract Specifications: cboe.com
- Cboe 0DTE product page: cboe.com/tradable_products/0dte
- Options Industry Council (OIC) Options Education: optionseducation.org
Disclosure: This article was produced with AI assistance and reviewed before publication. It is for informational purposes only and is not investment advice.