Implements \Drupal\Core\Form\FormInterface::submitForm().
Overrides SystemConfigFormBase::submitForm
public function submitForm(array &$form, array &$form_state) {
$this->configFactory
->get('system.date')
->set('country.default', $form_state['values']['site_default_country'])
->set('first_day', $form_state['values']['date_first_day'])
->save();
$this->configFactory
->get('system.timezone')
->set('default', $form_state['values']['date_default_timezone'])
->set('user.configurable', $form_state['values']['configurable_timezones'])
->set('user.warn', $form_state['values']['empty_timezone_message'])
->set('user.default', $form_state['values']['user_default_timezone'])
->save();
parent::submitForm($form, $form_state);
}