PHP date/time zones can be different from an installation to another. I would explore your available zones with a snippet like
<?php
$timezone_identifiers = DateTimeZone::listIdentifiers();
print_r($timezone_identifiers);
?>
to check whether your zone is available under another name. Alternatively, you can update your timedate zones database, as referred in http://www.php.net/manual/en/timezones.php