Currency exchange offices keep their own hours (many at airports operate 24/7), but foreign exchange rates are set by the global forex markets, which operate electronically — much like the stock exchanges.
Unlike stock exchanges, the forex market runs 24 hours a day, 5 days a week. The trading day is divided into three overlapping sessions — European, American, and Asian — based on the working hours of the major financial centers. The European session is anchored by London, the American session by New York, and the Asian session by Tokyo.
The standard hours for each session, expressed in GMT (UTC), are:
| Session | City | Open | Close |
| European | London | 08:00 | 17:00 |
| American | New York | 13:00 | 22:00 |
| Asian | Tokyo | 23:00 | 09:00 |
During the London – New York overlap (roughly 13:00–17:00 GMT), trading volume and liquidity peak, which tends to produce the tightest bid/ask spreads on major currency pairs.
The forex market is closed over the weekend: trading winds down at the New York close on Friday (22:00 GMT) and reopens with the Sydney / Tokyo session on Sunday evening GMT. Note that local session times shift by one hour when North America and Europe transition in and out of daylight saving time, since GMT itself does not observe DST.
The global forex markets are used primarily by banks, institutional investors, and large corporations that trade substantial amounts of currency every day. Retail traders typically access these rates through brokers that aggregate interbank pricing.