How Does the US Market Work
When are U.S. stock exchanges closed?
The major stock markets in the U.S. are only open for trading on normal business days only—Monday to Friday, except on holidays.
The NYSE and NASDAQ are closed for trading on the following holidays:
New Year's Day
Martin Luther King, Jr. Day
Presidents' Day (Washington's Birthday)
Good Friday
Memorial Day
Independence Day
Labor Day
Thanksgiving Day
Christmas Day
Seasonality can sometimes play a part in a trading strategy. Some holidays in the U.S. market provide periods of decreased trading volumes, as many investors and traders are busy with vacations and family plans. There tends to be little business news released right before a holiday, too.
The S&P 500 tends to trade at a loss on the last trading day of the year and gains on the first day of the new year. Trading days before and after Jan. 1 can be affected by tax gain/loss harvesting and portfolio rebalancing.
Source: NYSE, Investopedia