public function setCompletedOn($completed_on) {
        
        $this -> completed_on = $completed_on !== null ? new \DateTime($completed_on) : null;
        return $this;
    }
public function setCompletedOn($completed_on) {
        
        $this -> completed_on = $completed_on !== null ? new \DateTime($completed_on) : null;
        return $this;
    }
public function setCompletedOn ( $ completed_on ) { $ this -> completed_on = $ completed_on !== null ? new \ DateTime ( $ completed_on ) : null ; return $ this ; }
Sets the completed on
@param string $completed_on
@return TimestampAwareTrait
Sets the completed on