I recently realized that my understanding of U.S. stock market opening hours was a bit mixed up, especially when it comes to time differences and daylight saving time. While I’m organizing my notes, I’ll summarize these key points, which may be helpful for everyone.

U.S. stock market opening hours actually fall into three time periods. Regular trading is from 9:30 to 16:00 (U.S. Eastern Time), Monday through Friday—this is the main trading window. If you want to catch the early session, pre-market trading starts at 4:00 and runs until 9:30. After trading ends, there’s also an after-hours session from 16:00 to 20:00. Although liquidity is not as good as during regular hours, it’s still possible to trade.

For us Asian investors, the most important thing is to understand the time difference. Here’s a pitfall: the U.S. switches between daylight saving time and standard time, while we don’t. The U.S. starts daylight saving time on the second Sunday in March and ends it on the first Sunday in November. During daylight saving time, the U.S. stock market opening hours correspond to Beijing time from 21:30 to 4:00 a.m. the next day. During standard time, it’s one hour later, changing to 22:30 to 5:00 a.m. the next day. Even though this difference is only one hour, it can still make a big difference to your trading schedule.

Also, be sure to pay attention to the U.S. stock market holiday schedule. The U.S. has a number of statutory holidays, and on those days the stock market is closed outright. For example, New Year’s Day, Martin Luther King Jr. Day, Independence Day, Thanksgiving, and Christmas are all major holidays. There are also some days with early closures—for instance, the day before Independence Day and the day before Christmas are both early closed by three hours. If you don’t keep track of these market holidays, it’s easy to fall into a trap.

U.S. stocks are mainly traded on three venues: the New York Stock Exchange, NASDAQ, and the American Stock Exchange. The New York Stock Exchange is the largest. In the past, floor trading was very active, but nowadays it’s mostly electronic. NASDAQ is a bit special: it is entirely electronic, with especially many technology stocks listed. While these three exchanges operate independently, their opening and closing times are basically synchronized.

If you want to trade U.S. stocks frequently, make sure you clearly remember the U.S. stock market opening hours and the corresponding Beijing times. In particular, pay attention to the switch between daylight saving time and standard time, so you don’t realize at the last minute that you’ve miscalculated the time difference.