Forex (foreign exchange) markets are open 24 hours a day, five days a week, except for holidays. This is because currency trading does not occur on weekends and most national holidays.

The forex market is open for trading from Sunday at 5:00 PM EST (10:00 PM GMT) to Friday at 4:00 PM EST (9:00 PM GMT).

The forex market can be divided into four major trading sessions: the Sydney session, the Tokyo session, the London session, and the New York session.

The Sydney session: The Sydney session starts at 9:00 PM EST (2:00 AM GMT) and ends at 5:00 AM EST (10:00 AM GMT). This session is dominated by the Australian dollar, the New Zealand dollar, and the Japanese yen.

The Tokyo session: The Tokyo session starts at 7:00 PM EST (12:00 AM GMT) and ends at 4:00 AM EST (9:00 AM GMT). This session is dominated by the Japanese yen, the Australian dollar, and the New Zealand dollar.

The London session: The London session starts at 3:00 AM EST (8:00 AM GMT) and ends at 12:00 PM EST (5:00 PM GMT). This session is dominated by the British pound, the euro, and the Swiss franc.

The New York session: The New York session starts at 8:00 AM EST (1:00 PM GMT) and ends at 5:00 PM EST (10:00 PM GMT). This session is dominated by the US dollar, the Canadian dollar, and the Mexican peso.

It is important to note that these are rough estimates and that the actual trading hours may vary depending on various factors such as holidays and other events. Additionally, the forex market is highly liquid and can be traded at any time, so it is always possible to find buyers and sellers, even outside of the major trading sessions.