public function getInstallDate()
{
//get the composer.json file of the package to check its modified-date
$repository = $this->installedPackage->getRepository();
$reflection = new \ReflectionClass('Composer\\Repository\\FilesystemRepository');
$p = $reflection->getProperty('file');
$p->setAccessible(true);
$file = $p->getValue($repository);
$installDate = filemtime($file->getPath());
return \DateTime::createFromFormat('U', $installDate);
}
