diff --git a/core/modules/system/lib/Drupal/system/Tests/Datetime/DrupalDateTimeTest.php b/core/modules/system/lib/Drupal/system/Tests/Datetime/DrupalDateTimeTest.php
index 9673c9c..e576c8e 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Datetime/DrupalDateTimeTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Datetime/DrupalDateTimeTest.php
@@ -37,6 +37,15 @@ public function setUp() {
   }
 
   /**
+   * Test that the AJAX Timezone Callback can deal with various formats.
+   */
+  public function testSystemTimezone() {
+    // Query the AJAX Timezone Callback with a long-format date.
+    $response = $this->drupalGet('/system/timezone/BST/3600/1?date=Tue+Sep+17+2013+21%3A35%3A31+GMT%2B0100+(BST)#');
+    $this->assertEqual($response, '"Europe\/London"', 'Timezone AJAX callback successfully identifies and responds to a long-format date.');
+  }
+
+  /**
    * Test that DrupalDateTime can detect the right timezone to use.
    * Test with a variety of less commonly used timezone names to
    * help ensure that the system timezone will be different than the