public function isValid()
{
if (parent::isValid()) {
if (empty($this->format)) {
$this->_error('invalid_format', $this->format);
return False;
}
if (strptime($this->getValue(), $this->format) === False) {
$this->_error('invalid_date', $this->format);
return False;
}
$value = $this->getValue();
return empty($value) ? True : $this->passUserValidationRules();
}
return False;
}