protected function getExtra(AnalyticsOverview $overview)
    {
        $timespan = $overview->getTimespan() - $overview->getStartOffset();
        $extra = parent::getExtra($overview);

        if ($timespan <= 1) {
            $extra['dimensions'] = 'ga:date,ga:hour';
        } elseif ($timespan <= 7) {
            $extra['dimensions'] = 'ga:date,ga:hour';
        } elseif ($timespan <= 31) {
            $extra['dimensions'] = 'ga:week,ga:day,ga:date';
        } else {
            $extra['dimensions'] = 'ga:isoYearIsoWeek';
        }

        return $extra;
    }