diff --git a/core/lib/Drupal/Core/Datetime/FormattedDateDiff.php b/core/lib/Drupal/Core/Datetime/FormattedDateDiff.php
index 07bb83638b1549f4aac6dd3d9c8c6b4be9a1eac0..266022be83ed0149958d5761bf95c0f6eed86a80 100644
--- a/core/lib/Drupal/Core/Datetime/FormattedDateDiff.php
+++ b/core/lib/Drupal/Core/Datetime/FormattedDateDiff.php
@@ -51,10 +51,23 @@ public function getString() {
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function getCacheMaxAge() {
+    return $this->maxAge;
+  }
+
+  /**
+   * The maximum age for which this object may be cached.
+   *
    * @return int
+   *   The maximum time in seconds that this object may be cached.
+   *
+   * @deprecated in Drupal 8.1.9 and will be removed before Drupal 9.0.0. Use
+   *   \Drupal\Core\Datetime\FormattedDateDiff::getCacheMaxAge() instead.
    */
   public function getMaxAge() {
-    return $this->maxAge;
+    return $this->getCacheMaxAge();
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Core/Datetime/DateTest.php b/core/tests/Drupal/Tests/Core/Datetime/DateTest.php
index 238b5c88e3e8d44e806211374242d20c4a452daa..edf6d714e798c5ac8f4c3b270874481db1b29765 100644
--- a/core/tests/Drupal/Tests/Core/Datetime/DateTest.php
+++ b/core/tests/Drupal/Tests/Core/Datetime/DateTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\Core\Datetime;
 
+use Drupal\Core\Cache\CacheableMetadata;
 use Drupal\Core\Datetime\DateFormatter;
 use Drupal\Core\Datetime\FormattedDateDiff;
 use Drupal\Core\DependencyInjection\ContainerBuilder;
@@ -392,6 +393,38 @@ public function providerTestFormatDiff() {
     return $data;
   }
 
+  /**
+   * Tests FormattedDateDiff.
+   *
+   * @covers \Drupal\Core\Datetime\FormattedDateDiff::toRenderable
+   * @covers \Drupal\Core\Datetime\FormattedDateDiff::getString
+   * @covers \Drupal\Core\Datetime\FormattedDateDiff::getCacheMaxAge
+   */
+  public function testFormattedDateDiff() {
+    $string = '10 minutes';
+    $max_age = 60;
+    $object = new FormattedDateDiff($string, $max_age);
+
+    // Test conversion to a render array.
+    $expected = [
+      '#markup' => $string,
+      '#cache' => [
+        'max-age' => $max_age,
+      ],
+    ];
+    $this->assertArrayEquals($expected, $object->toRenderable());
+
+    // Test retrieving the formatted time difference string.
+    $this->assertEquals($string, $object->getString());
+
+    // Test applying cacheability data to an existing build.
+    $build = [];
+    CacheableMetadata::createFromObject($object)->applyTo($build);
+    $this->assertEquals($max_age, $build['#cache']['max-age']);
+    // Test the BC layer.
+    $this->assertSame($object->getCacheMaxAge(), $object->getMaxAge());
+  }
+
   /**
    * Creates a UNIX timestamp given a date and time string in the format
    * year-month-day hour:minute:seconds (e.g. 2013-12-11 10:09:08).