Overrides prepareTimezone().
Override basic component timezone handling to use Drupal's knowledge of the preferred user timezone.
Overrides DateTimePlus::prepareTimezone
protected function prepareTimezone($timezone) {
$user_timezone = drupal_get_user_timezone();
if (empty($timezone) && !empty($user_timezone)) {
$timezone = $user_timezone;
}
parent::prepareTimezone($timezone);
}