diff --git a/core/modules/datetime/datetime.module b/core/modules/datetime/datetime.module
index f25140f..cc19c39 100644
--- a/core/modules/datetime/datetime.module
+++ b/core/modules/datetime/datetime.module
@@ -14,8 +14,11 @@
 
 /**
  * Defines the format that date and time should be stored in.
+ *
+ * This is equivalent to 'c' for output, but also compatible with
+ * \DateTime::createFromFormat() for parsing purposes.
  */
-const DATETIME_DATETIME_STORAGE_FORMAT = 'Y-m-d\TH:i:s';
+const DATETIME_DATETIME_STORAGE_FORMAT = 'Y-m-d\TH:i:sP';
 
 /**
  * Defines the format that dates should be stored in.
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
index 3fac252..99ccea4 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
@@ -48,7 +48,7 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
         }
 
         // Create the ISO date in Universal Time.
-        $iso_date = $date->format("Y-m-d\TH:i:s") . 'Z';
+        $iso_date = $date->format("Y-m-d\TH:i:sP", array('timezone' => 'UTC'));
 
         $this->setTimeZone($date);
 
diff --git a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
index f07d564..1de9601 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldType/DateTimeItem.php
@@ -68,7 +68,7 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
         'value' => array(
           'description' => 'The date value.',
           'type' => 'varchar',
-          'length' => 20,
+          'length' => 25,
         ),
       ),
       'indexes' => array(
diff --git a/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php b/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php
index bba2c33..7f015fd 100644
--- a/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php
+++ b/core/modules/datetime/tests/src/Kernel/DateTimeItemTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Tests\datetime\Kernel;
 
+use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Field\FieldItemInterface;
 use Drupal\entity_test\Entity\EntityTest;
@@ -50,7 +51,7 @@ protected function setUp() {
   public function testDateTimeItem() {
     // Verify entity creation.
     $entity = EntityTest::create();
-    $value = '2014-01-01T20:00:00Z';
+    $value = '2014-01-01T20:00:00+00:00';
     $entity->field_datetime = $value;
     $entity->name->value = $this->randomMachineName();
     $entity->save();
@@ -85,7 +86,7 @@ public function testDateTimeItem() {
   public function testSetValue() {
     // Test DateTimeItem::setValue() using string.
     $entity = EntityTest::create();
-    $value = '2014-01-01T20:00:00Z';
+    $value = '2014-01-01T20:00:00+00:00';
     $entity->get('field_datetime')->set(0, $value);
     $entity->save();
     // Load the entity and ensure the field was saved correctly.
@@ -110,7 +111,7 @@ public function testSetValue() {
   public function testSetValueProperty() {
     // Test Date::setValue().
     $entity = EntityTest::create();
-    $value = '2014-01-01T20:00:00Z';
+    $value = '2014-01-01T20:00:00+00:00';
 
     $entity->set('field_datetime', $value);
     $entity->save();
@@ -120,4 +121,22 @@ public function testSetValueProperty() {
     $this->assertEqual($entity->field_datetime[0]->value, $value, '"Value" property can be set directly.');
   }
 
+  /**
+   * Tests setting the value with setDateTime()
+   */
+  public function testSetDateTime() {
+    $entity = EntityTest::create();
+    $value = '2014-01-01T20:00:00+00:00';
+    // 'c' isn't a valid format string per http://php.net/manual/en/datetime.createfromformat.php
+    // so build the format string from the parts.
+    $datetime = DrupalDateTime::createFromFormat('Y-m-d\TH:i:sP', $value);
+    $date_item = $entity->get('field_datetime')->appendItem();
+    $date_item->get('value')->setDateTime($datetime);
+    $entity->save();
+
+    $id = $entity->id();
+    $entity = entity_load('entity_test', $id);
+    $this->assertEqual($entity->field_datetime[0]->value, $value, '"Value" property can be set from DrupalDateTime object.');
+  }
+
 }
diff --git a/core/modules/rdf/tests/src/Kernel/Field/DateTimeFieldRdfaTest.php b/core/modules/rdf/tests/src/Kernel/Field/DateTimeFieldRdfaTest.php
index 012b57d..31cd298 100644
--- a/core/modules/rdf/tests/src/Kernel/Field/DateTimeFieldRdfaTest.php
+++ b/core/modules/rdf/tests/src/Kernel/Field/DateTimeFieldRdfaTest.php
@@ -21,7 +21,7 @@ class DateTimeFieldRdfaTest extends FieldRdfaTestBase {
    *
    * @var string
    */
-  protected $testValue = '2014-01-28T06:01:01';
+  protected $testValue = '2014-01-28T06:01:01+00:00';
 
   /**
   * {@inheritdoc}
@@ -48,6 +48,6 @@ protected function setUp() {
    * Tests the default formatter.
    */
   public function testDefaultFormatter() {
-    $this->assertFormatterRdfa(array('type' => 'datetime_default'), 'http://schema.org/dateCreated', array('value' => $this->testValue . 'Z', 'type' => 'literal', 'datatype' => 'http://www.w3.org/2001/XMLSchema#dateTime'));
+    $this->assertFormatterRdfa(array('type' => 'datetime_default'), 'http://schema.org/dateCreated', array('value' => $this->testValue, 'type' => 'literal', 'datatype' => 'http://www.w3.org/2001/XMLSchema#dateTime'));
   }
 }