Just took a look on 3.0.2 and 3.0.1 and this is the fix:
Open admin/applications/forums/modules_admin/statistics/stats.php and find:
'group' => $this->DB->buildDateFormat( $this->DB->buildFromUnixtime( $sql_field ), $sql_date ) . ", $sql_field",
Change to:
'group' => 'result_time',
Screenshot on 3.0.3: