Implements hook_form_FORM_ID_alter().
function system_form_user_register_form_alter(&$form, &$form_state) {
$config = config('system.date');
if ($config
->get('timezone.user.configurable') && $config
->get('timezone.user.default') == DRUPAL_USER_TIMEZONE_SELECT) {
system_user_timezone($form, $form_state);
return $form;
}
}