--- a/heuristics/dateHeuristics.php
+++ b/heuristics/dateHeuristics.php
@@ -40,10 +40,12 @@
 }
 
 function getStddevAverageContractPeriod() {
-    global $averageContractPeriod, $stddevContractPeriod;
-    $query = "select AVG(dateDiff(contractEnd,contractStart)),stddev(dateDiff(contractEnd,contractStart)) from contractnotice";
+    global $averageContractPeriod, $stddevContractPeriod,$conn;
+    $query = 'select AVG("contractEnd"-"contractStart"),stddev("contractEnd"-"contractStart") from contractnotice';
     $result = $conn->query($query);
+             databaseError($conn->errorInfo());
     $r = $result->fetch(PDO::FETCH_BOTH);
+
     $averageContractPeriod = $r[0];
     $stddevContractPeriod = $r[1];
 }
@@ -94,11 +96,13 @@
 
 function getDaysLate() {
 
-    global $averageDaysLate, $stddevDaysLate;
+    global $averageDaysLate, $stddevDaysLate,$conn;
 
-    $query = "select AVG(dateDiff(publishDate,contractStart)), STDDEV(dateDiff(publishDate,contractStart)) from contractnotice";
+    $query = 'select AVG(extract (day from "publishDate"-"contractStart")), STDDEV(extract (day from "publishDate"-"contractStart")) from contractnotice';
     $result = $conn->query($query);
+          databaseError($conn->errorInfo());
     $r = $result->fetch(PDO::FETCH_BOTH);
+
     $averageDaysLate = $r[0];
     $stddevDaysLate = $r[1];
 }