For most of options history, “0DTE” only existed on the day a weekly or monthly expiration happened to land. SPY changed that: it now lists expirations every trading day, Monday through Friday. There is always a contract that expires today.

What “0DTE” means

0DTE is “zero days to expiration” — an option that expires at the end of the current session. Because SPY now has one every day, you can take a same-day directional trade any weekday, not just on Fridays. That's the entire reason 0DTE SPY scalping became a daily strategy rather than an occasional one (0DTE trading, explained).

Why every-day 0DTE is a different animal

A same-day option lives at the extreme end of the greeks. Gamma is enormous, so the contract's delta swings violently on small moves. Theta is brutal and accelerates into the close, so being early or sitting in chop costs you even when you're right. The upside is fast; so is the downside. Daily availability makes it convenient — it does not make it gentle.

A fresh 0DTE every day is opportunity and hazard in the same package: maximum move-sensitivity riding on a clock that runs out by the bell.

The practical implications

Three things follow. First, you never have to reach for a longer-dated contract to trade today's move. Second, positions must be managed to the close — a 0DTE left open expires, and if it's in-the-money you face automatic exercise. Third, the tape itself is shaped by all that same-day gamma dealers are hedging, which is exactly what draws the day's dealer levels. Convenient to access, unforgiving to hold — trade it with a plan and an exit.