What was the date of the 2010 U.S. stock-market “Flash Crash”?

The 2010 U.S. stock-market Flash Crash occurred on May 6, 2010.

During the afternoon of May 6, major U.S. equity indexes dropped rapidly before recovering much of the loss. The Dow Jones Industrial Average fell nearly 1,000 points, or about 9%, within minutes, making it one of the most dramatic intraday disruptions in modern market history.

Investigations by U.S. regulators linked the event to a combination of market stress, high-frequency trading, and a large automated sell order. The precise interaction among trading algorithms, liquidity withdrawal, and order routing made the decline unusually fast.

The crash prompted new market controls, including expanded circuit breakers and mechanisms intended to prevent trades at clearly erroneous prices. It also showed that electronic markets can move much faster than human traders can react.