Knp\Bundle\KnpBundlesBundle\Entity\Activity::setCreatedAt PHP Method

    public function setCreatedAt(\DateTime $createdAt)
    {
        $this->createdAt = $createdAt;
    }

 /**
  * @return boolean|Bundle
  */
 public function tweet()
 {
     /* @var $trendingBundle Bundle*/
     if (!($trendingBundle = $this->em->getRepository('KnpBundlesBundle:Bundle')->findLatestTrend($this->twitterParams['idle_period']))) {
         throw new TrendingBundleNotFoundException();
     }
     $timestamp = time();
     $parameters = array('oauth_consumer_key' => $this->twitterParams['oauth_client_id'], 'oauth_timestamp' => $timestamp, 'oauth_nonce' => md5(microtime() . mt_rand()), 'oauth_version' => '1.0', 'oauth_signature_method' => 'HMAC-SHA1', 'oauth_token' => $this->twitterParams['oauth_token']);
     $parameters['oauth_signature'] = OAuthUtils::signRequest('POST', $this->twitterApiUrl, $parameters, $this->twitterParams['oauth_client_secret'], $this->twitterParams['oauth_token_secret']);
     $response = $this->httpRequest($this->twitterApiUrl, $this->prepareMessage($trendingBundle), $parameters, array(), 'POST');
     if ($response->isSuccessful()) {
         $trendingBundle->setLastTweetedAt(new \DateTime());
         $this->em->persist($trendingBundle);
         $activity = new Activity();
         $activity->setType(Activity::ACTIVITY_TYPE_TWEETED);
         $activity->setCreatedAt(new \DateTime());
         $activity->setBundle($trendingBundle);
         $this->em->persist($activity);
         $this->em->flush();
         return $trendingBundle;
     }
     return false;
 }