code: public function getDuration()
  	{
  		$executed = $this->getExecuted();
  		$finished = $this->getFinished();
  
  		if (is_null($executed) || is_null($finished)) {
  			return 0;
  		}
  
  		return strtotime($finished) - strtotime($executed);
  	}
docs: Returns duration of the job's execution.
  
  @return integer Time in seconds.
  @todo Implement this!