diff --git a/mod/quiz/lib.php b/mod/quiz/lib.php
index 7ce1e229afe..d783f987c27 100644
--- a/mod/quiz/lib.php
+++ b/mod/quiz/lib.php
@@ -1352,8 +1352,8 @@ function quiz_get_group_override_priorities($quizid) {
         }
     }
 
-    // Sort open times in descending manner. The earlier open time gets higher priority.
-    rsort($grouptimeopen);
+    // Sort open times in ascending manner. The earlier open time gets higher priority.
+    sort($grouptimeopen);
     // Set priorities.
     $opengrouppriorities = [];
     $openpriority = 1;
@@ -1361,8 +1361,8 @@ function quiz_get_group_override_priorities($quizid) {
         $opengrouppriorities[$timeopen] = $openpriority++;
     }
 
-    // Sort close times in ascending manner. The later close time gets higher priority.
-    sort($grouptimeclose);
+    // Sort close times in descending manner. The later close time gets higher priority.
+    rsort($grouptimeclose);
     // Set priorities.
     $closegrouppriorities = [];
     $closepriority = 1;
diff --git a/mod/quiz/tests/lib_test.php b/mod/quiz/tests/lib_test.php
index a260a05522b..8a54c36eb93 100644
--- a/mod/quiz/tests/lib_test.php
+++ b/mod/quiz/tests/lib_test.php
@@ -489,13 +489,13 @@ class mod_quiz_lib_testcase extends advanced_testcase {
 
         $openpriorities = $priorities['open'];
         // Override 2's time open has higher priority since it is sooner than override 1's.
-        $this->assertEquals(1, $openpriorities[$override1->timeopen]);
-        $this->assertEquals(2, $openpriorities[$override2->timeopen]);
+        $this->assertEquals(2, $openpriorities[$override1->timeopen]);
+        $this->assertEquals(1, $openpriorities[$override2->timeopen]);
 
         $closepriorities = $priorities['close'];
         // Override 1's time close has higher priority since it is later than override 2's.
-        $this->assertEquals(2, $closepriorities[$override1->timeclose]);
-        $this->assertEquals(1, $closepriorities[$override2->timeclose]);
+        $this->assertEquals(1, $closepriorities[$override1->timeclose]);
+        $this->assertEquals(2, $closepriorities[$override2->timeclose]);
     }
 
     public function test_quiz_core_calendar_provide_event_action_open() {