date_default_timezone_set Sets the default timezone used by all date/time functions in a script &reftitle.description; booldate_default_timezone_set stringtimezone_identifier date_default_timezone_set sets the default timezone used by all date/time functions. Since PHP 5.1.0 (when the date/time functions were rewritten), every call to a date/time function will generate a E_NOTICE if the timezone isn't valid, and/or a E_STRICT message if using the system settings or the TZ environment variable. &reftitle.parameters; timezone_identifier The timezone identifier, like UTC or Europe/Lisbon. The list of valid identifiers is available in the . &reftitle.returnvalues; This function always returns &true; (even if the timezone_identifier isn't valid). &reftitle.seealso; date_default_timezone_get