There is no forex exchange.
The spot forex market (the market which we trade) is a decentralized, off-exchange market, which is “open” everywhere in the world 24 hours per day, from 8am Monday morning in New Zealand (1900 GMT Sunday) until 5pm Friday afternoon in New York (2200 GMT Friday). That’s 123 hours per week that the retail spot forex market is “open”. Everywhere.
But, in every one of the principal forex market locations (London, New York, Tokyo, etc.) trading volume is heaviest during the [I]normal business hours[/I] in that location. As a rule of thumb, more than 80% of each day’s volume in each location occurs during normal business hours, and less than 20% of each day’s volume in each location occurs in the overnight period. These volume percentages are based on a 9-hour business day, 8am-5pm, in each location.
Because daily forex trading volume in each market location is so heavily concentrated in the 8am-5pm time period in that location, we refer to that 8am-5pm period as the “trading session” in that market.
There are many threads and posts here on this forum in which session times are discussed, and you can use the SEARCH feature at the top of this page (or any other forum page) to search the forum for everything ever written on that topic.
This thread might help to answer your questions — 301 Moved Permanently