diff --git a/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/ChangedTestItem.php b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/ChangedTestItem.php
index f429b39..0e0a46c 100644
--- a/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/ChangedTestItem.php
+++ b/core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldType/ChangedTestItem.php
@@ -31,11 +31,12 @@ public function preSave() {
       // During a test the request time is immutable. To allow tests of the
       // algorithm of
       // Drupal\Core\Field\Plugin\Field\FieldType\ChangedItem::preSave() we need
-      // to set a real time value here. But for the stability of the test,
-      // change the entity with the original language at the beginning of the
-      // second. Comply with this requirement on real sites do not need to.
+      // to set a real time value here. For the stability of the test, set the
+      // time of the original language to the current time plus just over one
+      // second to simulate two different request times.
+      // @todo mock the time service in https://www.drupal.org/node/2908210.
       if ($this->getEntity()->language()->isDefault()) {
-        // Wait 1.1 second's, because time_sleep_until works not very accurate.
+        // Wait 1.1 seconds because time_sleep_until() is not reliable.
         time_sleep_until(time() + 1.1);
       }
       $this->value = time();