public function byHours(int $hours): Date
    {
        return $this->hourTo($this->originalDate->hours() + $hours);
    }
public function byHours(int $hours): Date
    {
        return $this->hourTo($this->originalDate->hours() + $hours);
    }
public function byHours ( int $ hours ) : Date { return $ this -> hourTo ( $ this -> originalDate -> hours ( ) + $ hours ) ; }
changes date by given amount of hours

@api
@param   int  $hours
@return  \stubbles\date\Date
changes date by given amount of hours