One US trading day
US stock exchanges follow a daily schedule in New York time (Eastern Time, ET). Pre-market trading runs from 4:00 to 9:30. At 9:30 an opening auction sets the first price, then continuous trading runs until 16:00, when a closing auction sets the official closing price. After-hours trading continues until 20:00 with fewer participants and wider spreads.
Two kinds of safety brakes can stop trading. Limit up-limit down (LULD) bands pause a single stock for five minutes if its price stays outside a band around its recent average for more than 15 seconds. Market-wide circuit breakers halt every exchange when the S&P 500 falls 7% (Level 1) or 13% (Level 2) from the previous close; at 20% (Level 3) trading stops for the rest of the day. Individual stocks can also be halted while news is pending.
- Opening auction (9:30): collects orders and sets the opening price at the price that matches the most shares.
- Closing auction (16:00): sets the official closing price used by index funds and for end-of-day valuation.
- LULD pause: five minutes for one stock after the price stays outside its band for 15 seconds.
- Circuit breakers: market-wide halts at 7%, 13% and 20% declines of the S&P 500.
Lab · what's graded
- Phases of the day20 pts
- Halts and their triggers20 pts
- When does continuous trading start?10 pts
- Reasons for a halt15 pts
- A Level 2 circuit breaker15 pts
- Why the closing auction matters20 pts