diff --git a/htdocs/comm/action/index.php b/htdocs/comm/action/index.php
index d503c1bc71d..b56910bb89d 100644
--- a/htdocs/comm/action/index.php
+++ b/htdocs/comm/action/index.php
@@ -1729,11 +1729,24 @@ function dol_color_minus($color, $minus, $minusunit = 16)
  */
 function sort_events_by_date($a, $b)
 {
-	if($a->datep != $b->datep)
-	{
-		return $a->datep - $b->datep;
-	}
+    if($a->datep != $b->datep)
+    {
+        return $a->datep - $b->datep;
+    }
 
-	// If both events have the same start time, longest first
-	return $b->datef - $a->datef;
+    // If both events have the same start time, longest first
+    
+    if(! is_numeric($b->datef))
+    {
+        // when event B have no end timestamp, event B should sort be before event A (All day events on top)
+        return 1;
+    }
+
+    if(! is_numeric($a->datef))
+    {
+        // when event A have no end timestamp , event A should sort be before event B (All day events on top)
+        return -1;
+    }
+
+    return $b->datef - $a->datef;
 }