diff --git a/admin/intro.php b/admin/intro.php
index a3bb94f44..1e587d651 100644
--- a/admin/intro.php
+++ b/admin/intro.php
@@ -192,9 +192,7 @@ trigger_notify('loc_end_intro');
 // +-----------------------------------------------------------------------+
 
 $nb_weeks = $conf['dashboard_activity_nb_weeks'];
-$date = new DateTime();
-//Array for the JS tooltip
-$activity_last_weeks = array();
+
 //Count mondays
 $mondays = 0;
 //Get mondays number for the chart legend
@@ -202,48 +200,66 @@ $week_number = array();
 //Array for sorting days in circle size
 $temp_data = array();
 
-//Get data from $nb_weeks last weeks
-while ($mondays < $nb_weeks) 
+if (!isset($_SESSION['cache_activity_last_weeks']) or $_SESSION['cache_activity_last_weeks']['calculated_on'] < strtotime('5 minutes ago'))
 {
-  if ($date->format('D') == 'Mon') 
+  $activity_last_weeks = array();
+  $date = new DateTime();
+
+  //Get data from $nb_weeks last weeks
+  while ($mondays < $nb_weeks)
   {
-    $week_number[] = $date->format('W');
-    $mondays += 1;
-  }
-
-  $date->sub(new DateInterval('P1D'));
-}
-
-$week_number = array_reverse($week_number);
-
-$date_string = $date->format('Y-m-d');
-$query = '
-SELECT *
-  FROM `'.ACTIVITY_TABLE.'`
-  WHERE occured_on >= "'.$date_string.'%"
-;';
-
-$result = query2array($query, null);
-
-foreach ($result as $row) 
-{
-  $day_date = new DateTime($row['occured_on']);
-
-  $week = 0;
-  for ($i=0; $i < $nb_weeks; $i++) 
-  { 
-    if ($week_number[$i] == $day_date->format('W'))
+    if ($date->format('D') == 'Mon')
     {
-      $week = $i;
+      $week_number[] = $date->format('W');
+      $mondays += 1;
     }
-  }
-  $day_nb = $day_date->format('N');
 
-  @$activity_last_weeks[$week][$day_nb]['details'][ucfirst($row['object'])][ucfirst($row['action'])] += 1;
-  @$activity_last_weeks[$week][$day_nb]['number'] += 1;
-  @$activity_last_weeks[$week][$day_nb]['date'] = format_date($day_date->getTimestamp());
+    $date->sub(new DateInterval('P1D'));
+  }
+
+  $week_number = array_reverse($week_number);
+
+  $date_string = $date->format('Y-m-d');
+  $query = '
+  SELECT
+      DATE_FORMAT(occured_on , \'%Y-%m-%d\') AS activity_day,
+      object,
+      action,
+      COUNT(*) AS activity_counter
+    FROM `'.ACTIVITY_TABLE.'`
+    WHERE occured_on >= \''.$date_string.'\'
+    GROUP BY activity_day, object, action
+  ;';
+  $activity_actions = query2array($query);
+
+  foreach ($activity_actions as $action)
+  {
+    $day_date = new DateTime($action['activity_day']);
+
+    $week = 0;
+    for ($i=0; $i < $nb_weeks; $i++)
+    {
+      if ($week_number[$i] == $day_date->format('W'))
+      {
+        $week = $i;
+      }
+    }
+    $day_nb = $day_date->format('N');
+
+    @$activity_last_weeks[$week][$day_nb]['details'][ucfirst($action['object'])][ucfirst($action['action'])] = $action['activity_counter'];
+    @$activity_last_weeks[$week][$day_nb]['number'] += $action['activity_counter'];
+    @$activity_last_weeks[$week][$day_nb]['date'] = format_date($day_date->getTimestamp());
+  }
+
+  $_SESSION['cache_activity_last_weeks'] = array(
+    'calculated_on' => time(),
+    'data' => $activity_last_weeks,
+  );
 }
 
+$activity_last_weeks = $_SESSION['cache_activity_last_weeks']['data'];
+
+
 foreach($activity_last_weeks as $week => $i) 
 {
   foreach($i as $day => $j)