It is known that the Forex market allows trading round the clock, from Monday to Friday. On weekends and holidays, the markets are closed. In fact, trading hours are equivalent to the open time of banks. This is connected with the fact that this market does not work over the weekend (banks have also days off).
24-hour availability of the Forex work is possible due to the fact that the market is not tied to a specific region, but is available to all countries worldwide. Therefore, when the evening comes in one corner of the globe and the banks get closed, morning comes in the other part of the world and other banks open. This is the principle of continuity of work. This division of the world into zones depending on the time of day is referred to as "Trading Sessions". There are four main sessions and they come one after another, even overlapping for a short time.
Market sessions are an important element of trading hours, because they directly depend on the principle of work. After all, each session has its own nuances and characteristics, which are expressed in increasing or lowering volatility, higher volume in specific currency pairs, and so on.
As trade is conducted all over the world, it is necessary to base the data on a single timing, which would act as a standard. For a long time, GMT (Greenwich, London) has been such a standard. Currently, it is considered that this standard is out of date, and it was replaced by the UTC (Universal Coordinated Time) standard.
Here are the main four sessions, their largest exchanges and the working time: