diff --git a/core/lib/Drupal/Core/Datetime/Plugin/Field/FieldWidget/TimestampDatetimeWidget.php b/core/lib/Drupal/Core/Datetime/Plugin/Field/FieldWidget/TimestampDatetimeWidget.php
index d11cf54..dff27f5 100644
--- a/core/lib/Drupal/Core/Datetime/Plugin/Field/FieldWidget/TimestampDatetimeWidget.php
+++ b/core/lib/Drupal/Core/Datetime/Plugin/Field/FieldWidget/TimestampDatetimeWidget.php
@@ -29,7 +29,7 @@ class TimestampDatetimeWidget extends WidgetBase {
   public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
     $date_format = DateFormat::load('html_date')->getPattern();
     $time_format = DateFormat::load('html_time')->getPattern();
-    $default_value = isset($items[$delta]->value) ? DrupalDateTime::createFromTimestamp($items[$delta]->value) : '';
+    $default_value = isset($items[$delta]->value) && is_numeric($items[$delta]->value) ? DrupalDateTime::createFromTimestamp($items[$delta]->value) : '';
     $element['value'] = $element + array(
       '#type' => 'datetime',
       '#default_value' => $default_value,
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/ChangedItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/ChangedItem.php
index 9f2096f..9c53665 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/ChangedItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/ChangedItem.php
@@ -13,7 +13,7 @@
  *   label = @Translation("Last changed"),
  *   description = @Translation("An entity field containing a UNIX timestamp of when the entity has been last updated."),
  *   no_ui = TRUE,
- *   default_widget = "datetime_default",
+ *   default_widget = "datetime_timestamp",
  *   default_formatter = "timestamp",
  *   list_class = "\Drupal\Core\Field\ChangedFieldItemList"
  * )
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/CreatedItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/CreatedItem.php
index b4bcac5..d050bee 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/CreatedItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/CreatedItem.php
@@ -10,7 +10,7 @@
  *   label = @Translation("Created"),
  *   description = @Translation("An entity field containing a UNIX timestamp of when the entity has been created."),
  *   no_ui = TRUE,
- *   default_widget = "datetime_default",
+ *   default_widget = "datetime_timestamp",
  *   default_formatter = "timestamp"
  * )
  */
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/TimestampItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/TimestampItem.php
index 98094ca..5cc40f7 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/TimestampItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/TimestampItem.php
@@ -13,7 +13,7 @@
  *   id = "timestamp",
  *   label = @Translation("Timestamp"),
  *   description = @Translation("An entity field containing a UNIX timestamp value."),
- *   default_widget = "datetime_default",
+ *   default_widget = "datetime_timestamp",
  *   default_formatter = "timestamp",
  *   constraints = {
  *     "ComplexData" = {
diff --git a/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php b/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
new file mode 100644
index 0000000..205578a
--- /dev/null
+++ b/core/tests/Drupal/FunctionalTests/Datetime/TimestampTest.php
@@ -0,0 +1,107 @@
+<?php
+
+namespace Drupal\FunctionalTests\Datetime;
+
+use Drupal\Core\Entity\Entity\EntityFormDisplay;
+use Drupal\Core\Entity\Entity\EntityViewDisplay;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\Tests\BrowserTestBase;
+
+
+/**
+ * Tests the functionality of Timestamp core field UI.
+ *
+ * @group somegroup
+ */
+
+class TimestampTest extends BrowserTestBase {
+
+  /**
+   * An array of display options to pass to entity_get_display()
+   *
+   * @var array
+   */
+  protected $displayOptions;
+
+  /**
+   * A field storage to use in this test class.
+   *
+   * @var \Drupal\field\Entity\FieldStorageConfig
+   */
+  protected $fieldStorage;
+
+  /**
+   * The field used in this test class.
+   *
+   * @var \Drupal\field\Entity\FieldConfig
+   */
+  protected $field;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['node', 'entity_test', 'field_ui'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $web_user = $this->drupalCreateUser([
+      'access content',
+      'view test entity',
+      'administer entity_test content',
+      'administer entity_test form display',
+      'administer content types',
+      'administer node fields',
+    ]);
+
+    $this->drupalLogin($web_user);
+    $field_name = 'field_timestamp';
+    $type = 'timestamp';
+    $widget_type = 'datetime_timestamp';
+    $formatter_type = 'timestamp';
+
+    $this->fieldStorage = FieldStorageConfig::create([
+      'field_name' => $field_name,
+      'entity_type' => 'entity_test',
+      'type' => $type,
+    ]);
+    $this->fieldStorage->save();
+    $this->field = FieldConfig::create([
+      'field_storage' => $this->fieldStorage,
+      'bundle' => 'entity_test',
+      'required' => TRUE,
+    ]);
+    $this->field->save();
+
+    EntityFormDisplay::load('entity_test.entity_test.default')
+      ->setComponent($field_name, ['type' => $widget_type])
+      ->save();
+
+    $this->displayOptions = [
+      'type' => $formatter_type,
+      'label' => 'hidden',
+    ];
+
+    EntityViewDisplay::create([
+      'targetEntityType' => $this->field->getTargetEntityTypeId(),
+      'bundle' => $this->field->getTargetBundle(),
+      'mode' => 'full',
+      'status' => TRUE,
+    ])->setComponent($field_name, $this->displayOptions)
+      ->save();
+  }
+
+  /**
+   * Tests the "datetime_timestamp" widget
+   */
+  public function testWidget() {
+    $this->drupalGet('entity_test/add');
+
+    $this->fail('Write a real test');
+  }
+
+}