How 0DTE SPX options work

What makes 0DTE different from weekly options?

Time value disappears over hours instead of days, so theta dominates and gamma is at its largest. An at-the-money contract can double or halve on an index move of a few tenths of a percent.

That asymmetry cuts both ways: positions need defined risk, because the same convexity that produces the gain produces the loss.

Why does the expected move matter intraday?

The expected move is the range the option market has priced for the session. Comparing realised range against it tells you whether the session is under-delivering (premium sellers favoured) or over-delivering (buyers favoured).

Live SPX expected-move figures by expiry sit on the expected move page.

What does the US session look like from Riyadh?

What should be checked before a 0DTE session?

The priced expected move, where net gamma flips sign, which strikes carry the heaviest open interest, and the economic calendar. Those four together explain most of what the session's structure will allow.

This is analytics and education, not investment advice, and nothing here is a recommendation to trade any contract.