Options expiration calendar, and how much gamma expires

The dates ahead

Dates are rules, so they are known years ahead; a third Friday that is a market holiday moves to the Thursday. The same rows are on the market calendar beside the releases, and in the terminal's calendar panel.

How much gamma expired, by symbol · session of 2026-09-18

The white mark is the symbol's usual share on that weekday, the median of its earlier sessions of the same weekday (of every other session while there are fewer than two); amber is a day at least half again above it. The book is every expiry inside 45 days, near the money, read at 10:00 ET. History starts in September 2026 and grows by one session every evening.

SPX, the last 40 sessions

The SPX engine's book is today's expiry and the next three, so its share runs higher than a symbol's and is compared with its own history only. Each bar opens that session in the terminal, where the EXPIRING TODAY card shows the number moving through the day.

Questions

The next expiry-class date on this calendar is Wed, Sep 30, 2026. Monthly options expire on the third Friday of every month; the quarterly expiration, with the index futures and the index rebalances, is the third Friday of March, June, September and December. When that Friday is a market holiday the expiration moves to the Thursday.

The quarterly third Friday, when stock options, index options and index futures expire together and the S&P and Nasdaq-100 rebalances take effect at the close. The ES and NQ futures settle at that morning's open, as the AM-settled SPX monthly options do; trading volume moves to the next futures contract eight days earlier, on the roll Thursday.

From the option chain itself: the unsigned dealer gamma of the contracts that expire on the day, as a share of the unsigned gamma of every expiry inside 45 days, across the strikes near the money. It is read at 10:00 ET. It says how much of the book is about to disappear, not what price does afterwards, and each symbol is compared with its own recent sessions only.

The last session of March, June, September and December carries its own SPX expiry, and a large hedged-equity fund resets a three-leg SPX option collar on that day. The strikes of that collar are public in advance and are watched as levels through the quarter.