diff --git a/calendar/delete.php b/calendar/delete.php
index 9ca53742f19..4f72df71f05 100644
--- a/calendar/delete.php
+++ b/calendar/delete.php
@@ -55,7 +55,7 @@ if ($event->eventtype !== 'user' && $event->eventtype !== 'site') {
 $course = $DB->get_record('course', array('id'=>$courseid));
 require_login($course);
 if (!$course) {
-    $PAGE->set_context(get_context_instance(CONTEXT_SYSTEM)); //TODO: wrong
+    $PAGE->set_context(context_system::instance()); //TODO: wrong
 }
 
 // Check the user has the required capabilities to edit an event
diff --git a/calendar/export_execute.php b/calendar/export_execute.php
index 229868237da..f4cb51cf410 100644
--- a/calendar/export_execute.php
+++ b/calendar/export_execute.php
@@ -162,7 +162,7 @@ foreach($events as $event) {
         $ev->add_property('dtend', Bennu::timestamp_to_datetime($event->timestart + $event->timeduration));
     }
     if ($event->courseid != 0) {
-        $coursecontext = get_context_instance(CONTEXT_COURSE, $event->courseid);
+        $coursecontext = context_course::instance($event->courseid);
         $ev->add_property('categories', format_string($courses[$event->courseid]->shortname, true, array('context' => $coursecontext)));
     }
     $ical->add_component($ev);
diff --git a/calendar/lib.php b/calendar/lib.php
index 6cff2a30108..dcb5e8a987a 100644
--- a/calendar/lib.php
+++ b/calendar/lib.php
@@ -580,7 +580,7 @@ function calendar_add_event_metadata($event) {
         }
         $icon = $OUTPUT->pix_url('icon', $event->modulename) . '';
 
-        $context = get_context_instance(CONTEXT_COURSE, $module->course);
+        $context = context_course::instance($module->course);
         $fullname = format_string($coursecache[$module->course]->fullname, true, array('context' => $context));
 
         $event->icon = '<img height="16" width="16" src="'.$icon.'" alt="'.$eventtype.'" title="'.$modulename.'" style="vertical-align: middle;" />';
@@ -595,7 +595,7 @@ function calendar_add_event_metadata($event) {
     } else if($event->courseid != 0 && $event->courseid != SITEID && $event->groupid == 0) {          // Course event
         calendar_get_course_cached($coursecache, $event->courseid);
 
-        $context = get_context_instance(CONTEXT_COURSE, $event->courseid);
+        $context = context_course::instance($event->courseid);
         $fullname = format_string($coursecache[$event->courseid]->fullname, true, array('context' => $context));
 
         $event->icon = '<img height="16" width="16" src="'.$OUTPUT->pix_url('c/course') . '" alt="'.get_string('courseevent', 'calendar').'" style="vertical-align: middle;" />';
@@ -1374,7 +1374,7 @@ function calendar_set_filters(array $courseeventsfrom, $ignorefilters = false) {
 
         if (count($courseeventsfrom)==1) {
             $course = reset($courseeventsfrom);
-            if (has_any_capability($allgroupscaps, get_context_instance(CONTEXT_COURSE, $course->id))) {
+            if (has_any_capability($allgroupscaps, context_course::instance($course->id))) {
                 $coursegroups = groups_get_all_groups($course->id, 0, 0, 'g.id');
                 $group = array_keys($coursegroups);
             }
@@ -1430,7 +1430,7 @@ function calendar_edit_event_allowed($event) {
         return false;
     }
 
-    $sitecontext = get_context_instance(CONTEXT_SYSTEM);
+    $sitecontext = context_system::instance();
     // if user has manageentries at site level, return true
     if (has_capability('moodle/calendar:manageentries', $sitecontext)) {
         return true;
@@ -1698,14 +1698,14 @@ function calendar_get_allowed_types(&$allowed, $course = null) {
     $allowed->user = has_capability('moodle/calendar:manageownentries', get_system_context());
     $allowed->groups = false; // This may change just below
     $allowed->courses = false; // This may change just below
-    $allowed->site = has_capability('moodle/calendar:manageentries', get_context_instance(CONTEXT_COURSE, SITEID));
+    $allowed->site = has_capability('moodle/calendar:manageentries', context_course::instance(SITEID));
 
     if (!empty($course)) {
         if (!is_object($course)) {
             $course = $DB->get_record('course', array('id' => $course), '*', MUST_EXIST);
         }
         if ($course->id != SITEID) {
-            $coursecontext = get_context_instance(CONTEXT_COURSE, $course->id);
+            $coursecontext = context_course::instance($course->id);
             $allowed->user = has_capability('moodle/calendar:manageownentries', $coursecontext);
 
             if (has_capability('moodle/calendar:manageentries', $coursecontext)) {
@@ -1752,7 +1752,7 @@ function calendar_add_event_allowed($event) {
         return false;
     }
 
-    $sitecontext = get_context_instance(CONTEXT_SYSTEM);
+    $sitecontext = context_system::instance();
     // if user has manageentries at site level, always return true
     if (has_capability('moodle/calendar:manageentries', $sitecontext)) {
         return true;
@@ -1953,20 +1953,20 @@ class calendar_event {
 
         $context = null;
         if (isset($data->courseid) && $data->courseid > 0) {
-            $context =  get_context_instance(CONTEXT_COURSE, $data->courseid);
+            $context =  context_course::instance($data->courseid);
         } else if (isset($data->course) && $data->course > 0) {
-            $context =  get_context_instance(CONTEXT_COURSE, $data->course);
+            $context =  context_course::instance($data->course);
         } else if (isset($data->groupid) && $data->groupid > 0) {
             $group = $DB->get_record('groups', array('id'=>$data->groupid));
-            $context = get_context_instance(CONTEXT_COURSE, $group->courseid);
+            $context = context_course::instance($group->courseid);
         } else if (isset($data->userid) && $data->userid > 0 && $data->userid == $USER->id) {
-            $context =  get_context_instance(CONTEXT_USER, $data->userid);
+            $context =  context_user::instance($data->userid);
         } else if (isset($data->userid) && $data->userid > 0 && $data->userid != $USER->id &&
                    isset($data->instance) && $data->instance > 0) {
             $cm = get_coursemodule_from_instance($data->modulename, $data->instance, 0, false, MUST_EXIST);
-            $context =  get_context_instance(CONTEXT_COURSE, $cm->course);
+            $context =  context_course::instance($cm->course);
         } else {
-            $context =  get_context_instance(CONTEXT_USER);
+            $context =  context_user::instance();
         }
 
         return $context;
diff --git a/calendar/renderer.php b/calendar/renderer.php
index a2f8a7b9a90..60e3a743174 100644
--- a/calendar/renderer.php
+++ b/calendar/renderer.php
@@ -687,7 +687,7 @@ class core_calendar_renderer extends plugin_renderer_base {
             return '';
         }
 
-        if (has_capability('moodle/calendar:manageentries', get_context_instance(CONTEXT_SYSTEM)) && !empty($CFG->calendar_adminseesall)) {
+        if (has_capability('moodle/calendar:manageentries', context_system::instance()) && !empty($CFG->calendar_adminseesall)) {
             $courses = get_courses('all', 'c.shortname','c.id,c.shortname');
         } else {
             $courses = enrol_get_my_courses();
@@ -698,7 +698,7 @@ class core_calendar_renderer extends plugin_renderer_base {
         $courseoptions = array();
         $courseoptions[SITEID] = get_string('fulllistofcourses');
         foreach ($courses as $course) {
-            $coursecontext = get_context_instance(CONTEXT_COURSE, $course->id);
+            $coursecontext = context_course::instance($course->id);
             $courseoptions[$course->id] = format_string($course->shortname, true, array('context' => $coursecontext));
         }
 
diff --git a/calendar/set.php b/calendar/set.php
index c02069e07d7..255027e5610 100644
--- a/calendar/set.php
+++ b/calendar/set.php
@@ -53,7 +53,7 @@ if ($courseid != -1) {
 }
 $url = new moodle_url('/calendar/set.php', array('return'=>base64_encode($return->out(false)), 'course' => $courseid, 'var'=>$var, 'sesskey'=>sesskey()));
 $PAGE->set_url($url);
-$PAGE->set_context(get_context_instance(CONTEXT_SYSTEM));
+$PAGE->set_context(context_system::instance());
 
 switch($var) {
     case 'showgroups':
diff --git a/cohort/edit_form.php b/cohort/edit_form.php
index a030ce20232..fe3ce492461 100644
--- a/cohort/edit_form.php
+++ b/cohort/edit_form.php
@@ -93,12 +93,12 @@ class cohort_edit_form extends moodleform {
         $parentlist = array();
         make_categories_list($displaylist, $parentlist, 'moodle/cohort:manage');
         $options = array();
-        $syscontext = get_context_instance(CONTEXT_SYSTEM);
+        $syscontext = context_system::instance();
         if (has_capability('moodle/cohort:manage', $syscontext)) {
             $options[$syscontext->id] = print_context_name($syscontext);
         }
         foreach ($displaylist as $cid=>$name) {
-            $context = get_context_instance(CONTEXT_COURSECAT, $cid, MUST_EXIST);
+            $context = context_coursecat::instance($cid, MUST_EXIST);
             $options[$context->id] = $name;
         }
         // always add current - this is not likely, but if the logic gets changed it might be a problem
diff --git a/cohort/index.php b/cohort/index.php
index 9c18bb72f01..026bcb855e9 100644
--- a/cohort/index.php
+++ b/cohort/index.php
@@ -37,7 +37,7 @@ require_login();
 if ($contextid) {
     $context = get_context_instance_by_id($contextid, MUST_EXIST);
 } else {
-    $context = get_context_instance(CONTEXT_SYSTEM);
+    $context = context_system::instance();
 }
 
 if ($context->contextlevel != CONTEXT_COURSECAT and $context->contextlevel != CONTEXT_SYSTEM) {
diff --git a/cohort/lib.php b/cohort/lib.php
index 367b19ec9de..ce512729766 100644
--- a/cohort/lib.php
+++ b/cohort/lib.php
@@ -110,14 +110,14 @@ function cohort_delete_category($category) {
     global $DB;
     // TODO: make sure that cohorts are really, really not used anywhere and delete, for now just move to parent or system context
 
-    $oldcontext = get_context_instance(CONTEXT_COURSECAT, $category->id, MUST_EXIST);
+    $oldcontext = context_coursecat::instance($category->id, MUST_EXIST);
 
     if ($category->parent and $parent = $DB->get_record('course_categories', array('id'=>$category->parent))) {
-        $parentcontext = get_context_instance(CONTEXT_COURSECAT, $parent->id, MUST_EXIST);
+        $parentcontext = context_coursecat::instance($parent->id, MUST_EXIST);
         $sql = "UPDATE {cohort} SET contextid = :newcontext WHERE contextid = :oldcontext";
         $params = array('oldcontext'=>$oldcontext->id, 'newcontext'=>$parentcontext->id);
     } else {
-        $syscontext = get_context_instance(CONTEXT_SYSTEM);
+        $syscontext = context_system::instance();
         $sql = "UPDATE {cohort} SET contextid = :newcontext WHERE contextid = :oldcontext";
         $params = array('oldcontext'=>$oldcontext->id, 'newcontext'=>$syscontext->id);
     }
@@ -165,7 +165,7 @@ function cohort_remove_member($cohortid, $userid) {
 function cohort_get_visible_list($course) {
     global $DB, $USER;
 
-    $context = get_context_instance(CONTEXT_COURSE, $course->id, MUST_EXIST);
+    $context = context_course::instance($course->id, MUST_EXIST);
     list($esql, $params) = get_enrolled_sql($context);
     $parentsql = get_related_contexts_string($context);
 
diff --git a/filter/algebra/algebradebug.php b/filter/algebra/algebradebug.php
index 67b715cc9ab..e133df159b6 100644
--- a/filter/algebra/algebradebug.php
+++ b/filter/algebra/algebradebug.php
@@ -15,7 +15,7 @@
     require_once($CFG->dirroot.'/filter/tex/lib.php');
 
     require_login();
-    require_capability('moodle/site:config', get_context_instance(CONTEXT_SYSTEM));
+    require_capability('moodle/site:config', context_system::instance());
 
     $query = urldecode($_SERVER['QUERY_STRING']);
 
diff --git a/filter/algebra/filter.php b/filter/algebra/filter.php
index 54ffaff5185..9ba698a55c9 100644
--- a/filter/algebra/filter.php
+++ b/filter/algebra/filter.php
@@ -73,7 +73,7 @@ function filter_algebra_image($imagefile, $tex= "", $height="", $width="", $alig
     }
     $anchorcontents .= "\" $style />";
 
-    if (!file_exists("$CFG->dataroot/filter/algebra/$imagefile") && has_capability('moodle/site:config', get_context_instance(CONTEXT_SYSTEM))) {
+    if (!file_exists("$CFG->dataroot/filter/algebra/$imagefile") && has_capability('moodle/site:config', context_system::instance())) {
         $link = '/filter/algebra/algebradebug.php';
         $action = null;
     } else {
diff --git a/filter/tex/filter.php b/filter/tex/filter.php
index 0b62fc1e189..0999df263a4 100644
--- a/filter/tex/filter.php
+++ b/filter/tex/filter.php
@@ -92,7 +92,7 @@ function filter_text_image($imagefile, $tex, $height, $width, $align, $alt) {
     }
     $anchorcontents .= "\" $style/>";
 
-    if (!file_exists("$CFG->dataroot/filter/tex/$imagefile") && has_capability('moodle/site:config', get_context_instance(CONTEXT_SYSTEM))) {
+    if (!file_exists("$CFG->dataroot/filter/tex/$imagefile") && has_capability('moodle/site:config', context_system::instance())) {
         $link = '/filter/tex/texdebug.php';
         $action = null;
     } else {
diff --git a/filter/tex/texdebug.php b/filter/tex/texdebug.php
index b4a08dee34c..32004492a24 100644
--- a/filter/tex/texdebug.php
+++ b/filter/tex/texdebug.php
@@ -40,7 +40,7 @@
     $texexp = optional_param('tex', '', PARAM_RAW);
 
     require_login();
-    require_capability('moodle/site:config', get_context_instance(CONTEXT_SYSTEM), $USER->id); /// Required cap to run this. MDL-18552
+    require_capability('moodle/site:config', context_system::instance(), $USER->id); /// Required cap to run this. MDL-18552
 
     $output = '';