What time does the stock market open?

The US cash equity day is 09:30 to 16:00 Eastern - but the full trading day is much longer than that.

The headline answer is 09:30 ET, when continuous trading begins on NYSE and Nasdaq. But that's only the regular cash session. The full picture:

04:00 ET - pre-market trading opens. Low volume, wide spreads, but where overnight news first registers.
09:30 ET - opening bell. The opening auction sets the official open print.
16:00 ET - closing bell. The closing auction is typically the highest-volume minute of the day.
20:00 ET - after-hours trading ends.

For other countries: London opens at 08:00 GMT, Frankfurt at 09:00 CET, Tokyo at 09:00 JST, and Hong Kong at 09:30 HKT. The live homepage shows them all in your local clock.