diff --git a/includes/pages/user_shifts.php b/includes/pages/user_shifts.php
index e5fd27ef..206a1586 100644
--- a/includes/pages/user_shifts.php
+++ b/includes/pages/user_shifts.php
@@ -37,8 +37,18 @@ function user_shifts() {
  *          The shiftfilter to update.
  */
 function update_ShiftsFilter_timerange(ShiftsFilter $shiftsFilter, $days) {
-  $shiftsFilter->setStartTime(check_request_datetime('start_day', 'start_time', $days, time()));
-  $shiftsFilter->setEndTime(check_request_datetime('end_day', 'end_time', $days, time() + 24 * 60 * 60));
+  $start_time = $shiftsFilter->getStartTime();
+  if ($start_time == null) {
+    $start_time = time();
+  }
+  
+  $end_time = $shiftsFilter->getEndTime();
+  if ($end_time == null) {
+    $end_time = $start_time + 24 * 60 * 60;
+  }
+  
+  $shiftsFilter->setStartTime(check_request_datetime('start_day', 'start_time', $days, $start_time));
+  $shiftsFilter->setEndTime(check_request_datetime('end_day', 'end_time', $days, $end_time));
   
   if ($shiftsFilter->getStartTime() > $shiftsFilter->getEndTime()) {
     $shiftsFilter->setEndTime($shiftsFilter->getStartTime() + 24 * 60 * 60);
@@ -57,18 +67,10 @@ function update_ShiftsFilter_timerange(ShiftsFilter $shiftsFilter, $days) {
  */
 function update_ShiftsFilter(ShiftsFilter $shiftsFilter, $user_shifts_admin, $days) {
   $shiftsFilter->setUserShiftsAdmin($user_shifts_admin);
-  if (isset($_REQUEST['filled'])) {
-    $shiftsFilter->setFilled(check_request_int_array('filled'));
-  }
-  if (isset($_REQUEST['rooms'])) {
-    $shiftsFilter->setRooms(check_request_int_array('rooms'));
-  }
-  if (isset($_REQUEST['types'])) {
-    $shiftsFilter->setTypes(check_request_int_array('types'));
-  }
-  if ((isset($_REQUEST['start_time']) && isset($_REQUEST['start_day']) && isset($_REQUEST['end_time']) && isset($_REQUEST['end_day'])) || $shiftsFilter->getStartTime() == null || $shiftsFilter->getEndTime() == null) {
-    update_ShiftsFilter_timerange($shiftsFilter, $days);
-  }
+  $shiftsFilter->setFilled(check_request_int_array('filled', $shiftsFilter->getFilled()));
+  $shiftsFilter->setRooms(check_request_int_array('rooms', $shiftsFilter->getRooms()));
+  $shiftsFilter->setTypes(check_request_int_array('types', $shiftsFilter->getTypes()));
+  update_ShiftsFilter_timerange($shiftsFilter, $days);
 }
 
 function load_rooms() {
diff --git a/includes/sys_page.php b/includes/sys_page.php
index 713dd33b..102be926 100644
--- a/includes/sys_page.php
+++ b/includes/sys_page.php
@@ -89,12 +89,14 @@ function select_array($data, $key_name, $value_name) {
  *
  * @param String $name
  *          Name of the request param
+ * @param array<int> $default
+ *          Default return value, if param is not set
  */
-function check_request_int_array($name) {
+function check_request_int_array($name, $default = []) {
   if (isset($_REQUEST[$name]) && is_array($_REQUEST[$name])) {
     return array_filter($_REQUEST[$name], 'is_numeric');
   }
-  return [];
+  return $default;
 }
 
 /**
diff --git a/includes/view/ShiftCalendarRenderer.php b/includes/view/ShiftCalendarRenderer.php
index 151a39e0..d25f4048 100644
--- a/includes/view/ShiftCalendarRenderer.php
+++ b/includes/view/ShiftCalendarRenderer.php
@@ -19,7 +19,7 @@ class ShiftCalendarRenderer {
    * Distance between two shifts in pixels
    */
   const MARGIN = 5;
-  
+
   /**
    * Seconds added to the start and end time
    */
@@ -56,12 +56,12 @@ class ShiftCalendarRenderer {
     
     foreach ($shifts as $shift) {
       $room_id = $shift['RID'];
+      $header = Room_name_render([
+          'RID' => $room_id,
+          'Name' => $shift['room_name'] 
+      ]);
       if (! isset($lanes[$room_id])) {
         // initialize room with one lane
-        $header = Room_name_render([
-            'RID' => $room_id,
-            'Name' => $shift['room_name'] 
-        ]);
         $lanes[$room_id] = [
             new ShiftCalendarLane($header, $this->getFirstBlockStartTime(), $this->getBlocksPerSlot()) 
         ];
@@ -108,6 +108,9 @@ class ShiftCalendarRenderer {
    * @return the generated html
    */
   public function render() {
+    if (count($this->lanes) == 0) {
+      return '';
+    }
     return div('shift-calendar', [
         $this->renderTimeLane(),
         $this->renderShiftLanes()