The Forex world market is different from any other financial trading market in that it is open 24 hours a day. Of course this is only true in the business week, but from Monday morning (or Sunday evening in many time zones) through Friday afternoon it is open non stop and you can trade at any time. This is because the Forex market does not operate in any one fixed place. It involves all of the world currencies and trading is possible during business hours in all time zones. This covers the whole 24 hours.
However, if you are actively involved in Forex trading you will want to know more than this. You will need to know what are the best times to trade, since the market is not equally active 24 hours a day. You might also want to know the precise times of the opening and closing at the beginning and end of the week, and the different session times in the biggest financial centers.
You may know that the international date line runs down the Pacific Ocean, with Asia and Australasia on one side and the American continent on the other. New Zealand is one of the first countries to begin the new day, with eastern Australia following. So when the financial center in Sydney opens for business at 8 am on Monday morning, it is 5 pm Sunday in New York and 2 pm Sunday in California. There can be some variations because of different time settings in summer, but broadly speaking this means that if you live in the western states of the USA you can start your trading week right after Sunday lunch.
At the end of the week, the last major market to close in the Forex world is New York at 4 pm EST Friday. The financial floor in Chicago will stay open later, as will some of the South American countries, but currency trading for the week pretty much dies down right around the New York close. Now that is going to be a lot later in places further east. It is 9 pm in London and if you live in Sydney, you can trade right through to 7 am Saturday, eastern Australian time.
So what are the best times to trade? If you are involved in long term trading where you might leave a trade open for a week or more, it may not matter too much. However, if you are into day trading and scalping you will want to be in the market at the busiest times.
The two most active trading floors in the world are New York and London. So you will not be surprised to hear that the busiest time for currency trading is when both of these two are open. They overlap for just three hours a day. In New York this is the morning (8 am to 11 am) and in London it is the afternoon (1 pm to 4 pm). Translate that period to your own time zone if you do not live in the EST or British time zones, and you will know the best time for you to get online to trade in the forex world market.