Which one to use Each zone is identified by the city with the largest population in a specific area. Zones are divided into 10 major groups: Africa, America, Antarctica, Artic, Asia, Atlantic, Europe, Indian, Pacific. Examples are: America/Toronto, Europe/Berlin, America/New_York, Europe/Oslo, Asia/Singapore. There is also a group "Others" which contains outdated and backwards compatible names, such as Canada/Eastern, Etc/GMT-1 and US/Central. Those should *not* be used. Pick the zone that is closest to your location. http://php.net/timezones