diff --git a/lib/tests/behat/behat_transformations.php b/lib/tests/behat/behat_transformations.php
index 7e4fd490b4c..cd5c4a41221 100644
--- a/lib/tests/behat/behat_transformations.php
+++ b/lib/tests/behat/behat_transformations.php
@@ -167,8 +167,8 @@ class behat_transformations extends behat_base {
 
         $count = count($timepassed);
         if ($count === 2) {
-            // If timestamp with spcified format, then retrun date.
-            return date($timepassed[1], $timestamp);
+            // If timestamp with specified strftime format, then return formatted date string.
+            return userdate($timestamp, $timepassed[1]);
         } else if ($count === 1) {
             return $timestamp;
         } else {
diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index 5b12b8c6816..214b7b246c9 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -48,6 +48,9 @@ information provided here is intended especially for developers.
   those fields. This replaces existing functions get_extra_user_fields(), get_extra_user_fields_sql(),
   get_user_field_name(), get_all_user_name_fields(), and user_picture::fields(), which have all been
   deprecated.
+* The behat transformation 'string time to timestamp' no longer supports datetime format. If provided, the format must
+  be strftime compatible. Example:
+    - I should see "##tomorrow noon##%A, %d %B %Y, %I:%M %p##"
 
 === 3.10 ===
 * PHPUnit has been upgraded to 8.5. That comes with a few changes: