diff --git a/calendar/event.php b/calendar/event.php
index fd2e1f24b5b..43304352e60 100644
--- a/calendar/event.php
+++ b/calendar/event.php
@@ -50,10 +50,13 @@
         redirect(CALENDAR_URL.'view.php?view=upcoming');
     }
 
-    $action    = required_param('action', PARAM_ALPHA);
-    $eventid   = optional_param('id', 0, PARAM_INT);
+    $action = required_param('action', PARAM_ALPHA);
+    $eventid = optional_param('id', 0, PARAM_INT);
     $eventtype = optional_param('type', 'select', PARAM_ALPHA);
     $urlcourse = optional_param('course', 0, PARAM_INT);
+    $cal_y = optional_param('cal_y');
+    $cal_m = optional_param('cal_m');
+    $cal_d = optional_param('cal_d');
 
     if(!$site = get_site()) {
         redirect($CFG->wwwroot.'/'.$CFG->admin.'/index.php');
@@ -361,20 +364,17 @@
         break;
 
         case 'new':
-            optional_variable($_GET['cal_y']);
-            optional_variable($_GET['cal_m']);
-            optional_variable($_GET['cal_d']);
-            optional_variable($form->timestart, -1);
+            set_default($form->timestart, -1);
 
-            if($_GET['cal_y'] && $_GET['cal_m'] && $_GET['cal_d'] && checkdate($_GET['cal_m'], $_GET['cal_d'], $_GET['cal_y'])) {
-                $form->timestart = make_timestamp($_GET['cal_y'], $_GET['cal_m'], $_GET['cal_d'], 0, 0, 0);
+            if($cal_y && $cal_m && $cal_d && checkdate($cal_m, $cal_d, $cal_y)) {
+                $form->timestart = make_timestamp($cal_y, $cal_m, $cal_d, 0, 0, 0);
             }
-            else if($_GET['cal_y'] && $_GET['cal_m'] && checkdate($_GET['cal_m'], 1, $_GET['cal_y'])) {
-                if($_GET['cal_y'] == $now['year'] && $_GET['cal_m'] == $now['mon']) {
-                    $form->timestart = make_timestamp($_GET['cal_y'], $_GET['cal_m'], $now['mday'], 0, 0, 0);
+            else if($cal_y && $cal_m && checkdate($cal_m, 1, $cal_y)) {
+                if($cal_y == $now['year'] && $cal_m == $now['mon']) {
+                    $form->timestart = make_timestamp($cal_y, $cal_m, $now['mday'], 0, 0, 0);
                 }
                 else {
-                    $form->timestart = make_timestamp($_GET['cal_y'], $_GET['cal_m'], 1, 0, 0, 0);
+                    $form->timestart = make_timestamp($cal_y, $cal_m, 1, 0, 0, 0);
                 }
             }
             if($form->timestart < 0) {
diff --git a/calendar/lib.php b/calendar/lib.php
index 1610b449606..cc170f831eb 100644
--- a/calendar/lib.php
+++ b/calendar/lib.php
@@ -628,6 +628,8 @@ function calendar_filter_controls($type, $vars = NULL, $course = NULL) {
 
     $groupevents = true;
     $getvars = '';
+   
+    $id = optional_param( 'id',0,PARAM_INT );
 
     switch($type) {
         case 'event':
@@ -637,8 +639,8 @@ function calendar_filter_controls($type, $vars = NULL, $course = NULL) {
             $getvars = '&amp;from='.$type;
         break;
         case 'course':
-            if (isset($_GET['id'])) {
-                $getvars = '&amp;from=course&amp;id='.$_GET['id'];
+            if (isset_param('id')) {
+                $getvars = '&amp;from=course&amp;id='.$id;
             } else {
                 $getvars = '&amp;from=course';
             }
diff --git a/calendar/set.php b/calendar/set.php
index 86e3c4d3d9f..2c3f018ee66 100644
--- a/calendar/set.php
+++ b/calendar/set.php
@@ -41,20 +41,20 @@
     require_once('../config.php');
     require_once($CFG->dirroot.'/calendar/lib.php');
 
-    require_variable($_GET['from']);
-    require_variable($_GET['var']);
-    optional_variable($_GET['value']);
-    optional_variable($_GET['id']);
-    optional_variable($_GET['cal_d']);
-    optional_variable($_GET['cal_m']);
-    optional_variable($_GET['cal_y']);
+    $from = required_param('from');
+    $var = required_param('var');
+    $value = optional_param('value');
+    $id = optional_param('id');
+    $cal_d = optional_param('cal_d');
+    $cal_m = optional_param('cal_m');
+    $cal_y = optional_param('cal_y');
 
-    switch($_GET['var']) {
+    switch($var) {
         case 'setuser':
             // Not implemented yet (or possibly at all)
         break;
         case 'setcourse':
-            $id = intval($_GET['id']);
+            $id = intval($id);
             if($id == 0) {
                 $SESSION->cal_courses_shown = array();
                 calendar_set_referring_course(0);
@@ -94,21 +94,21 @@
         break;
     }
 
-    switch($_GET['from']) {
+    switch($from) {
         case 'event':
-            redirect(CALENDAR_URL.'event.php?action='.$_GET['action'].'&amp;type='.$_GET['type'].'&amp;id='.intval($_GET['id']));
+            redirect(CALENDAR_URL.'event.php?action='.$action.'&amp;type='.$type.'&amp;id='.intval($id));
         break;
         case 'month':
-            redirect(CALENDAR_URL.'view.php?view=month&cal_d='.$_GET['cal_d'].'&cal_m='.$_GET['cal_m'].'&cal_y='.$_GET['cal_y']);
+            redirect(CALENDAR_URL.'view.php?view=month&cal_d='.$cal_d.'&cal_m='.$cal_m.'&cal_y='.$cal_y);
         break;
         case 'upcoming':
             redirect(CALENDAR_URL.'view.php?view=upcoming');
         break;
         case 'day':
-            redirect(CALENDAR_URL.'view.php?view=day&cal_d='.$_GET['cal_d'].'&cal_m='.$_GET['cal_m'].'&cal_y='.$_GET['cal_y']);
+            redirect(CALENDAR_URL.'view.php?view=day&cal_d='.$cal_d.'&cal_m='.$cal_m.'&cal_y='.$cal_y);
         break;
         case 'course':
-            redirect($CFG->wwwroot.'/course/view.php?id='.intval($_GET['id']));
+            redirect($CFG->wwwroot.'/course/view.php?id='.intval($id));
         break;
         default:
 
diff --git a/calendar/view.php b/calendar/view.php
index 8281b07adf5..a80b7564b40 100644
--- a/calendar/view.php
+++ b/calendar/view.php
@@ -44,7 +44,11 @@
     require_once($CFG->dirroot.'/course/lib.php');
     require_once($CFG->dirroot.'/calendar/lib.php');
 
-    optional_variable($_GET['course'], 0);
+    $course = optional_param('course', 0);
+    $view = optional_param('view', 'upcoming');
+    $day  = optional_param('cal_d', 0, PARAM_INT);
+    $mon  = optional_param('cal_m', 0, PARAM_INT);
+    $yr   = optional_param('cal_y', 0, PARAM_INT);
 
     if(!$site = get_site()) {
         redirect($CFG->wwwroot.'/'.$CFG->admin.'/index.php');
@@ -56,10 +60,6 @@
 
     $nav = calendar_get_link_tag(get_string('calendar', 'calendar'), CALENDAR_URL.'view.php?view=upcoming&amp;', $now['mday'], $now['mon'], $now['year']);
 
-    $view = optional_param('view', 'upcoming');
-    $day  = optional_param('cal_d', 0, PARAM_INT);
-    $mon  = optional_param('cal_m', 0, PARAM_INT);
-    $yr   = optional_param('cal_y', 0, PARAM_INT);
     
     if(!checkdate($mon, $day, $yr)) {
         $day = intval($now['mday']);
@@ -83,8 +83,8 @@
     }
 
     // If a course has been supplied in the URL, change the filters to show that one
-    if (!empty($_GET['course'])) {
-        if ($course = get_record('course', 'id', $_GET['course'])) {
+    if (!empty($course)) {
+        if ($course = get_record('course', 'id', $course)) {
             if ($course->id == 1) {
                 // If coming from the home page, show all courses
                 $SESSION->cal_courses_shown = calendar_get_default_courses(true);