diff --git a/core/lib/Drupal/Component/Datetime/DateTimePlus.php b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
index 1d8bbb77ff4b0c7f721fff4c7b160d098f18a3e7..1d71ae6b384658c0ea7937c61092979d11f13ab6 100644
--- a/core/lib/Drupal/Component/Datetime/DateTimePlus.php
+++ b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
@@ -294,6 +294,30 @@ public function __call($method, $args) {
     return call_user_func_array(array($this->dateTimeObject, $method), $args);
   }
 
+  /**
+   * Returns the difference between two DateTimePlus objects.
+   *
+   * @param \Drupal\Component\Datetime\DateTimePlus|\DateTime $datetime2
+   *    The date to compare to.
+   * @param bool $absolute
+   *    Should the interval be forced to be positive?
+   *
+   * @return \DateInterval
+   *    A DateInterval object representing the difference between the two dates.
+   *
+   * @throws \BadMethodCallException
+   *    If the input isn't a DateTime or DateTimePlus object.
+   */
+  public function diff($datetime2, $absolute = FALSE) {
+    if ($datetime2 instanceof DateTimePlus) {
+      $datetime2 = $datetime2->dateTimeObject;
+    }
+    if (!($datetime2 instanceof \DateTime)) {
+      throw new \BadMethodCallException(sprintf('Method %s expects parameter 1 to be a \DateTime or \Drupal\Component\Datetime\DateTimePlus object', __METHOD__));
+    }
+    return $this->dateTimeObject->diff($datetime2, $absolute);
+  }
+
   /**
    * Implements the magic __callStatic method.
    *
diff --git a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
index 7f5e200caea67deeff71cac88b150d16bab4c391..d4cd751e5836f3a767e84c58b4f71d2366a7bda3 100644
--- a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
+++ b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
@@ -55,6 +55,42 @@ public function testDateArrays($input, $timezone, $expected) {
     $this->assertEquals($expected, $value, sprintf("Test new DateTimePlus(%s, %s): should be %s, found %s.", $input, $timezone, $expected, $value));
   }
 
+  /**
+   * Test date diffs.
+   *
+   * @param mixed $input1
+   *   A DateTimePlus object.
+   * @param mixed $input2
+   *   Date argument for DateTimePlus::diff method.
+   * @param bool $absolute
+   *   Absolute flag for DateTimePlus::diff method.
+   * @param \DateInterval $expected
+   *   The expected result of the DateTimePlus::diff operation.
+   *
+   * @dataProvider providerTestDateDiff
+   */
+  public function testDateDiff($input1, $input2, $absolute, \DateInterval $expected) {
+    $interval = $input1->diff($input2, $absolute);
+    $this->assertEquals($interval, $expected);
+  }
+
+  /**
+   * Test date diff exception caused by invalid input.
+   *
+   * @param mixed $input1
+   *   A DateTimePlus object.
+   * @param mixed $input2
+   *   Date argument for DateTimePlus::diff method.
+   * @param bool $absolute
+   *   Absolute flag for DateTimePlus::diff method.
+   *
+   * @dataProvider providerTestInvalidDateDiff
+   */
+  public function testInvalidDateDiff($input1, $input2, $absolute) {
+    $this->setExpectedException(\BadMethodCallException::class, 'Method Drupal\Component\Datetime\DateTimePlus::diff expects parameter 1 to be a \DateTime or \Drupal\Component\Datetime\DateTimePlus object');
+    $interval = $input1->diff($input2, $absolute);
+  }
+
   /**
    * Test creating dates from invalid array input.
    *
@@ -528,4 +564,106 @@ public function providerTestDateTimestamp() {
     );
   }
 
+  /**
+   * Provides data for date tests.
+   *
+   * @return array
+   *   An array of arrays, each containing the input parameters for
+   *   DateTimePlusTest::testDateDiff().
+   *
+   * @see DateTimePlusTest::testDateDiff()
+   */
+  public function providerTestDateDiff() {
+
+    $empty_interval = new \DateInterval('PT0S');
+
+    $positive_19_hours = new \DateInterval('PT19H');
+
+    $positive_18_hours = new \DateInterval('PT18H');
+
+    $positive_1_hour = new \DateInterval('PT1H');
+
+    $negative_1_hour = new \DateInterval('PT1H');
+    $negative_1_hour->invert = 1;
+
+    return array(
+      // There should be a 19 hour time interval between
+      // new years in Sydney and new years in LA in year 2000.
+      array(
+        'input2' => DateTimePlus::createFromFormat('Y-m-d H:i:s', '2000-01-01 00:00:00', new \DateTimeZone('Australia/Sydney')),
+        'input1' => DateTimePlus::createFromFormat('Y-m-d H:i:s', '2000-01-01 00:00:00', new \DateTimeZone('America/Los_Angeles')),
+        'absolute' => FALSE,
+        'expected' => $positive_19_hours,
+      ),
+      // In 1970 Sydney did not observe daylight savings time
+      // So there is only a 18 hour time interval.
+      array(
+        'input2' => DateTimePlus::createFromFormat('Y-m-d H:i:s', '1970-01-01 00:00:00', new \DateTimeZone('Australia/Sydney')),
+        'input1' => DateTimePlus::createFromFormat('Y-m-d H:i:s', '1970-01-01 00:00:00', new \DateTimeZone('America/Los_Angeles')),
+        'absolute' => FALSE,
+        'expected' => $positive_18_hours,
+      ),
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 3600, new \DateTimeZone('America/Los_Angeles')),
+        'input2' => DateTimePlus::createFromFormat('U', 0, new \DateTimeZone('UTC')),
+        'absolute' => FALSE,
+        'expected' => $negative_1_hour,
+      ),
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 3600),
+        'input2' => DateTimePlus::createFromFormat('U', 0),
+        'absolute' => FALSE,
+        'expected' => $negative_1_hour,
+      ),
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 3600),
+        'input2' => \DateTime::createFromFormat('U', 0),
+        'absolute' => FALSE,
+        'expected' => $negative_1_hour,
+      ),
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 3600),
+        'input2' => DateTimePlus::createFromFormat('U', 0),
+        'absolute' => TRUE,
+        'expected' => $positive_1_hour,
+      ),
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 3600),
+        'input2' => \DateTime::createFromFormat('U', 0),
+        'absolute' => TRUE,
+        'expected' => $positive_1_hour,
+      ),
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 0),
+        'input2' => DateTimePlus::createFromFormat('U', 0),
+        'absolute' => FALSE,
+        'expected' => $empty_interval,
+      ),
+    );
+  }
+
+  /**
+   * Provides data for date tests.
+   *
+   * @return array
+   *   An array of arrays, each containing the input parameters for
+   *   DateTimePlusTest::testInvalidDateDiff().
+   *
+   * @see DateTimePlusTest::testInvalidDateDiff()
+   */
+  public function providerTestInvalidDateDiff() {
+    return array(
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 3600),
+        'input2' => '1970-01-01 00:00:00',
+        'absolute' => FALSE,
+      ),
+      array(
+        'input1' => DateTimePlus::createFromFormat('U', 3600),
+        'input2' => NULL,
+        'absolute' => FALSE,
+      ),
+    );
+  }
+
 }
diff --git a/core/tests/Drupal/Tests/Core/Datetime/DrupalDateTimeTest.php b/core/tests/Drupal/Tests/Core/Datetime/DrupalDateTimeTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..e77542bc7b55f05d988bd7b30c24426441bacd68
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Datetime/DrupalDateTimeTest.php
@@ -0,0 +1,159 @@
+<?php
+
+namespace Drupal\Tests\Core\Datetime;
+
+use Drupal\Core\Datetime\DrupalDateTime;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\Core\Datetime\DrupalDateTime
+ * @group Datetime
+ */
+class DrupalDateTimeTest extends UnitTestCase {
+
+  /**
+   * Test date diffs.
+   *
+   * @param mixed $input1
+   *   A DrupalDateTime object.
+   * @param mixed $input2
+   *   Date argument for DrupalDateTime::diff method.
+   * @param bool $absolute
+   *   Absolute flag for DrupalDateTime::diff method.
+   * @param \DateInterval $expected
+   *   The expected result of the DrupalDateTime::diff operation.
+   *
+   * @dataProvider providerTestDateDiff
+   */
+  public function testDateDiff($input1, $input2, $absolute, \DateInterval $expected) {
+    $interval = $input1->diff($input2, $absolute);
+    $this->assertEquals($interval, $expected);
+  }
+
+  /**
+   * Test date diff exception caused by invalid input.
+   *
+   * @param mixed $input1
+   *   A DateTimePlus object.
+   * @param mixed $input2
+   *   Date argument for DateTimePlus::diff method.
+   * @param bool $absolute
+   *   Absolute flag for DateTimePlus::diff method.
+   *
+   * @dataProvider providerTestInvalidDateDiff
+   */
+  public function testInvalidDateDiff($input1, $input2, $absolute) {
+    $this->setExpectedException(\BadMethodCallException::class, 'Method Drupal\Component\Datetime\DateTimePlus::diff expects parameter 1 to be a \DateTime or \Drupal\Component\Datetime\DateTimePlus object');
+    $interval = $input1->diff($input2, $absolute);
+  }
+
+  /**
+   * Provides data for date tests.
+   *
+   * @return array
+   *   An array of arrays, each containing the input parameters for
+   *   DrupalDateTimeTest::testDateDiff().
+   *
+   * @see DrupalDateTimeTest::testDateDiff()
+   */
+  public function providerTestDateDiff() {
+
+    $settings = ['langcode' => 'en'];
+
+    $utc_tz = new \DateTimeZone('UTC');
+
+    $empty_interval = new \DateInterval('PT0S');
+
+    $positive_19_hours = new \DateInterval('PT19H');
+
+    $positive_18_hours = new \DateInterval('PT18H');
+
+    $positive_1_hour = new \DateInterval('PT1H');
+
+    $negative_1_hour = new \DateInterval('PT1H');
+    $negative_1_hour->invert = 1;
+
+    return array(
+
+      // There should be a 19 hour time interval between
+      // new years in Sydney and new years in LA in year 2000.
+      array(
+        'input2' => DrupalDateTime::createFromFormat('Y-m-d H:i:s', '2000-01-01 00:00:00', new \DateTimeZone('Australia/Sydney'), $settings),
+        'input1' => DrupalDateTime::createFromFormat('Y-m-d H:i:s', '2000-01-01 00:00:00', new \DateTimeZone('America/Los_Angeles'), $settings),
+        'absolute' => FALSE,
+        'expected' => $positive_19_hours,
+      ),
+      // In 1970 Sydney did not observe daylight savings time
+      // So there is only a 18 hour time interval.
+      array(
+        'input2' => DrupalDateTime::createFromFormat('Y-m-d H:i:s', '1970-01-01 00:00:00', new \DateTimeZone('Australia/Sydney'), $settings),
+        'input1' => DrupalDateTime::createFromFormat('Y-m-d H:i:s', '1970-01-01 00:00:00', new \DateTimeZone('America/Los_Angeles'), $settings),
+        'absolute' => FALSE,
+        'expected' => $positive_18_hours,
+      ),
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 3600, new \DateTimeZone('America/Los_Angeles'), $settings),
+        'input2' => DrupalDateTime::createFromFormat('U', 0, $utc_tz, $settings),
+        'absolute' => FALSE,
+        'expected' => $negative_1_hour,
+      ),
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 3600, $utc_tz, $settings),
+        'input2' => DrupalDateTime::createFromFormat('U', 0, $utc_tz, $settings),
+        'absolute' => FALSE,
+        'expected' => $negative_1_hour,
+      ),
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 3600, $utc_tz, $settings),
+        'input2' => \DateTime::createFromFormat('U', 0),
+        'absolute' => FALSE,
+        'expected' => $negative_1_hour,
+      ),
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 3600, $utc_tz, $settings),
+        'input2' => DrupalDateTime::createFromFormat('U', 0, $utc_tz, $settings),
+        'absolute' => TRUE,
+        'expected' => $positive_1_hour,
+      ),
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 3600, $utc_tz, $settings),
+        'input2' => \DateTime::createFromFormat('U', 0),
+        'absolute' => TRUE,
+        'expected' => $positive_1_hour,
+      ),
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 0, $utc_tz, $settings),
+        'input2' => DrupalDateTime::createFromFormat('U', 0, $utc_tz, $settings),
+        'absolute' => FALSE,
+        'expected' => $empty_interval,
+      ),
+    );
+  }
+
+  /**
+   * Provides data for date tests.
+   *
+   * @return array
+   *   An array of arrays, each containing the input parameters for
+   *   DateTimePlusTest::testInvalidDateDiff().
+   *
+   * @see DateTimePlusTest::testInvalidDateDiff()
+   */
+  public function providerTestInvalidDateDiff() {
+    $settings = ['langcode' => 'en'];
+    $utc_tz = new \DateTimeZone('UTC');
+    return array(
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 3600, $utc_tz, $settings),
+        'input2' => '1970-01-01 00:00:00',
+        'absolute' => FALSE,
+      ),
+      array(
+        'input1' => DrupalDateTime::createFromFormat('U', 3600, $utc_tz, $settings),
+        'input2' => NULL,
+        'absolute' => FALSE,
+      ),
+    );
+  }
+
+}