What is After-Hours Trading?
After-hours trading is buying and selling stocks after the regular market session ends. US exchanges are open 9:30 a.m. to 4:00 p.m. Eastern, and extended-hours trading runs before the open and after the close.
Why it matters
Earnings are often released after the close, so prices can move sharply in extended hours. Fewer participants trade then, so spreads are wider and prices can be more erratic.