For the Histogram panel, if Time Correction is set to UTC or Browser, it doesn’t reflect on tooltip, Tooltip always shows Browser mode.

Origin Banana Implementation
 $tooltip
              .html(
                group + dashboard.numberWithCommas(value) + " @ " + moment(item.datapoint[0]).format('MM/DD HH:mm:ss')
              )
              .place_tt(pos.pageX, pos.pageY);

Changed implementation
 var tooltipTime = moment(item.datapoint[0]).format('MM/DD HH:mm:ss');
              if(scope.panel.timezone === 'utc') {
                  tooltipTime = moment.utc(item.datapoint[0]).format('MM/DD HH:mm:ss');
              }
            $tooltip
              .html(
                group + dashboard.numberWithCommas(value) + " @ " + tooltipTime
              )