could::getStartDateDelta

public function getStartDateDelta()
{
	/** @var DateTime[] $dataOrig */
	$dataOrig = $this->getDataPristine();

	if(!is_object($dataOrig['START_DATE_PLAN']) || !is_object($this->data['START_DATE_PLAN']))
	{
		return INF;
	}

	return $this->data['START_DATE_PLAN']->getTimestamp() - $dataOrig['START_DATE_PLAN']->getTimestamp();
}