What is a Trading Day
A trading day is a day when the New York Stock Exchange (NYSE) is open, and you can buy and sell stocks or other commodities. The stock exchanges, NYSE included, are opened Monday through Friday except for fixed date holidays, which we will discuss further below. The regular trading hours (or the ore trading session) on such days are between 9:30 a.m. ET and 9:30 a.m. ET. Every once in a while, there are cases when a trading day begins at regular hours but closes earlier than usual - this is what's called a shortened trading day.
Besides the regular trading hours, there are pre-market trading sessions (7:00 a.m. to 9:30 a.m. ET) and after-hours sessions (4:00 p.m. to 8:00 p.m. ET). These are known as extended trading hours; only a few brokers allow trading during these intervals.