protected function parseReferenceDate($referenceDateString)
{
$referenceDateParts = explode('/', $referenceDateString, 2);
if (count($referenceDateParts) === 1) {
// assume a valid Date/Time string
return new \DateTime($referenceDateParts[0]);
}
// check if the period (the interval) is the first or second item:
if (strpos($referenceDateParts[0], 'P') === 0) {
$interval = new \DateInterval($referenceDateParts[0]);
$date = new \DateTime($referenceDateParts[1]);
return $date->sub($interval);
} elseif (strpos($referenceDateParts[1], 'P') === 0) {
$interval = new \DateInterval($referenceDateParts[1]);
$date = new \DateTime($referenceDateParts[0]);
return $date->add($interval);
} else {
throw new InvalidValidationOptionsException(sprintf('There is no valid interval declaration in "%s". Exactly one part must begin with "P".', $referenceDateString), 1324314462);
}
}
