Backend\Core\Engine\Form::isCorrect PHP Method

    public function isCorrect($revalidate = true)
    {
        return parent::isCorrect($revalidate);
    }

 /**
  * @return bool
  */
 private function isValid()
 {
     $fields = $this->form->getFields();
     if (!$fields['start_date']->isFilled(Language::err('FieldIsRequired')) || !$fields['end_date']->isFilled(Language::err('FieldIsRequired'))) {
         return $this->form->isCorrect();
     }
     if (!$fields['start_date']->isValid(Language::err('DateIsInvalid')) || !$fields['end_date']->isValid(Language::err('DateIsInvalid'))) {
         return $this->form->isCorrect();
     }
     $newStartDate = Model::getUTCTimestamp($fields['start_date']);
     $newEndDate = Model::getUTCTimestamp($fields['end_date']);
     // startdate cannot be before 2005 (earliest valid google startdate)
     if ($newStartDate < mktime(0, 0, 0, 1, 1, 2005)) {
         $fields['start_date']->setError(Language::err('DateRangeIsInvalid'));
     }
     // enddate cannot be in the future
     if ($newEndDate > time()) {
         $fields['start_date']->setError(Language::err('DateRangeIsInvalid'));
     }
     // enddate cannot be before the startdate
     if ($newStartDate > $newEndDate) {
         $fields['start_date']->setError(Language::err('DateRangeIsInvalid'));
     }
     return $this->form->isCorrect();
 }