A day in the US stock market
The regular session on the New York Stock Exchange and Nasdaq opens at 9:30 a.m. US Eastern Time and closes at 4:00 p.m. That is six and a half hours with no lunch break. Before it comes the pre-market session and after it the after-hours session, together called extended hours. A daily candle is usually built from regular-session trades only, while minute and hourly charts may include or exclude extended hours depending on the settings. So the same stock can show a different open, high and low depending on which chart you are looking at.
Converting to Korean time
Korea does not use daylight saving time and the US does, so the time difference between the two countries changes twice a year. US daylight saving time starts on the second Sunday in March and ends on the first Sunday in November. During that period Korea is 13 hours ahead of US Eastern Time, and 14 hours ahead the rest of the year. In the week the clocks change, it is common to set alerts or trading plans an hour off, so marking those dates on a calendar helps.
- Regular session during daylight saving: 10:30 p.m. to 5:00 a.m. the next day, Korean time
- Regular session outside daylight saving: 11:30 p.m. to 6:00 a.m. the next day, Korean time
- After-hours trading continues into the early Korean morning
- Europe changes its clocks on different dates from the US, so for a few weeks the Europe and US gap also differs from usual
Pre-market and after-hours
Pre-market trading happens before the regular session opens and after-hours trading after it closes. Pre-market often starts in the early Eastern morning and after-hours often runs until about 8:00 p.m., but the hours you can actually trade and the order types allowed differ by broker. Extended hours have few participants, so the spread between bid and ask is wide and even small orders can move the price a lot. When earnings or economic data come out before or after the session, a big candle appears first on the extended-hours chart, but there is no guarantee that price carries straight into the regular open. It is safer to treat extended-hours prices as a hint about direction.
How the chart behaves through the day
Even within the regular session, the chart tends to look different at different times of day. These are widely described general patterns and can vary by day and by stock.
- Right after the open: orders and news from overnight arrive at once, so volume is high and candles are long
- Midday: trading thins and prices often drift in a narrow range
- Near the close: orders that wrap up the day pile in and volume picks up again
- Extended hours: thin trading makes long wicks and sudden jumps more likely
Daily candle dates and Korean dates
A US daily candle carries the US date. Seen from Korea, one day's candle is built across two Korean dates. A US Monday candle, for example, starts on Monday night in Korea and ends early Tuesday morning. If you line up Korean and US stocks by the same date and forget this one-day shift, you can read cause and effect in the wrong order. The US also has different market holidays from Korea, and on some days around holidays the regular session closes early. Exchanges announce holidays and early closes each year, so check them in advance.
Chart settings to check
If the same stock shows different numbers in two places, the cause is usually one of the settings below. Checking them before reading a chart saves a lot of confusion.
- Extended hours on or off: including them changes intraday highs, lows and moving averages
- Display time zone: US Eastern Time or Korean time
- Bar basis: whether daily candles use the regular session only
- Data delay: free quotes can lag by several minutes
Check it with this site's live tools
The world markets overview shows which markets are open right now along with the current level of major indexes, so you can tell at a glance whether the US market is open during the Korean night. The large-cap scanner shows daily changes and indicators for major Korean and US stocks in one table, and the buy and sell signals tool shows each indicator's rule and current value for a chosen stock. Prices in these tools come from a data provider and may be delayed, and the way extended hours are handled may differ from your broker's screen.
Things to keep in mind
This guide explains time concepts for reading US stock charts and is not investment advice. Trading hours, extended-hours windows and market holidays can change and are run differently by different brokers, so check the official information from the exchange and your broker before placing an order. Remember too that extended-hours trading can be volatile and orders may not fill.
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