public function setFromQDateTime(QDateTime $dttFrom, QDateTime $dttTo)
    {
        $this->add($dttFrom->difference($dttTo));
    }
public function setFromQDateTime(QDateTime $dttFrom, QDateTime $dttTo)
    {
        $this->add($dttFrom->difference($dttTo));
    }
public function setFromQDateTime ( QDateTime $ dttFrom , QDateTime $ dttTo ) { $ this -> add ( $ dttFrom -> difference ( $ dttTo ) ) ; }
Sets current DateTimeSpan to the difference between two QDateTime objects

@param QDateTime $dttFrom
@param QDateTime $dttTo
Sets current DateTimeSpan to the difference between two QDateTime objects