A market holiday is a day when a stock exchange is closed for trading, typically due to a national public holiday or religious observance. Each country's exchanges follow their own holiday calendar, which means markets in different countries are often open and closed on different days. The NYSE observes 9 full holidays per year, while Japan's exchanges close for approximately 18 days, making it the most holiday-heavy major exchange. Market holidays can create gaps in price data and affect trading strategies that depend on continuous market access. Some exchanges also have early close days where trading ends before the normal closing time, such as the day after Thanksgiving in the US when markets close at 1:00 PM ET. For international investors, keeping track of multiple holiday calendars is essential to avoid placing orders on closed exchanges and to anticipate potential gap risk when markets reopen.