The Forex market is open for trading 24-hour a day from Sunday 22:00 GMT to Friday 22:00 GMT divided into four major trading sessions:

Timezone (Summer)EDTGMT
Sydney Open/Close 6:00 PM 3:00 AM 10:00 PM 7:00 AM
Tokyo Open/Close 7:00 PM 4:00 AM 11:00 PM 8:00 AM
London Open/Close 3:00 AM 12:00 PM 7:00 AM 4:00 PM
New York Open/Close 8:00 AM 5:00 PM 12:00 PM 9:00 PM

As you may notice, there is a period of time where 2 sessions are overlapping, since they are open at the same trading hours.

Here are the times when two trading sessions overlap:
  • New York and London: from 8am to 12am (EST)
  • Sydney and Tokyo: from 7pm to 2am
  • London and Tokyo markets overlap one hour, from 3am to 4am

The above time periods are considered to be the busiest ones, for the reason that there is more volume when two markets are open at the matching time. Through this period of time, more and more trading deals are been held, meaning more funds are being exchanged. Note that Sydney open shifts 2 hours.

Hypothetically the session open would only move by 1 hour when New York changes to standard time, however when New York moves 1 hour back, Sydney actually moves forward by 1 hour as the seasons are opposite in Australia.