default GMT offset or timezone string. Must be either a valid offset (-12 to 14) or a valid timezone string (America/New_York). See https://www.php.net/manual/en/timezones.php for all timezone strings currently supported by PHP. Important: When a previous timezone string, like `Europe/Kiev`, has been superseded by an updated one, like `Europe/Kyiv`, as a rule of thumb, the **old** timezone name should be used in the “translation” to allow for the default timezone setting to be PHP cross-version compatible, as old timezone names will be recognized in new PHP versions, while new timezone names cannot be recognized in old PHP versions. To verify which timezone strings are available in the _oldest_ PHP version supported, you can use https://3v4l.org/6YQAt#v5.6.20 and replace the “BR” (Brazil) in the code line with the country code for which you want to look up the supported timezone names.

Default start of the week. 0 = Sunday, 1 = Monday.