The global FOREX market trades 24 hours a day, except weekends. The week begins at 5:00 P.M. Eastern Standard Time on Sunday in Asia and ends at 3:00 P.M. Eastern Standard Time on Friday in New York.
The trading day begins in Asia (the Asian session), moves to Europe (the European session), and ends in North America (the North American session).
As a trader, you can participate any time you like, for as long as you like. Most part-time traders try to establish session times to meet their schedules. Others, such as this author, more or less always have their foot in the door.
This ability to check-in and out any time you like is a great attraction to the part-time trader.