Random article: Forex Market Trading Hours
The main feature of global Forex market is that there is no centralized ground for holding trades as it for example takes place in stock market. All market players (banks, investment funds, hedge funds, insurance companies, brokers etc.) work in different time zones around the globe. As the result, rate fluctuation keep going all the time.
Official time of market operation is 24 hours, 5 days a week from 8 p.m on Sunday till 11 p.m of Friday (UTC/GMT). Exception is state holidays when all financial bodies are out of duty. On holidays Forex market works unofficially as well but because of the low liquidity and activity volumes, it is rather hard to find liquidity suppliers on the market. During that time all financial operations take place between various financial entities, banks and more often upon urgent issues.