diff --git a/core/modules/datetime/src/Tests/DateTestBase.php b/core/modules/datetime/src/Tests/DateTestBase.php
index be210e7..a234ae0 100644
--- a/core/modules/datetime/src/Tests/DateTestBase.php
+++ b/core/modules/datetime/src/Tests/DateTestBase.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\datetime\Tests;
 
+@trigger_error('\Drupal\datetime\Tests\DateTestBase is deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0. Use \Drupal\Tests\BrowserTestBase instead. See https://www.drupal.org/node/2780063.', E_USER_DEPRECATED);
+
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Entity\Entity\EntityFormDisplay;
 use Drupal\Core\Entity\Entity\EntityViewDisplay;
@@ -15,7 +17,7 @@
  * Provides a base class for testing Datetime field functionality.
  *
  * @deprecated in Drupal 8.4.0 and will be removed before Drupal 9.0.0.
- *   Use \Drupal\Tests\BrowserTestBase.
+ *   Use \Drupal\Tests\BrowserTestBase instead.
  */
 abstract class DateTestBase extends WebTestBase {