public function validate($messageManager)
 {
     $field = $this->form->getField($this->fieldName);
     $fieldValue = $field->getValue();
     if (!is_null($fieldValue)) {
         if (date('Y-m-d', strtotime($fieldValue)) < CoreUtils::getDate()) {
             $messageManager->addMessage('dateInThePast', array($this->fieldName => $field->getCaption()));
         }
     }
 }