Forex markets trades around the clock all over the world. For this reason, it is broadly divided into three trading sessions that become active when certain areas of the world are open for business.
The first of these sessions is the Asian session. It includes the trading activity of the significant Asian centres, like Japan and China but also includes Australia, New Zealand and Russia.
Broadly speaking the Asian session begins at around 11 pm (GMT) the night before and continues all the way through until 8 am (GMT).