diff --git a/edit-mode/function/ganttConfig.js b/edit-mode/function/ganttConfig.js
index a9f9410..d7f317f 100644
--- a/edit-mode/function/ganttConfig.js
+++ b/edit-mode/function/ganttConfig.js
@@ -494,7 +494,18 @@ gantt.templates.task_end_date = function(date){
 gantt.templates.rightside_text = function (start, end, task) {
 	if (task.planned_end) {
 		if (end.getTime() > task.planned_end.getTime()) {
-			var overdue = Math.ceil(Math.abs((end.getTime() - task.planned_end.getTime()) / (24 * 60 * 60 * 1000)));
+      var plannedEndDate = gantt.calculateEndDate({
+          start_date: task.start_date,
+          duration: gantt.calculateDuration({
+              start_date: task.start_date,
+              end_date: task.planned_end
+          })
+      });
+      var overdue = gantt.calculateDuration({
+          start_date: plannedEndDate,
+          end_date: end,
+          task: task
+      }, 'day');
 			var text = "<b>Overdue: " + overdue + " days</b>";
 			return text;
 		}