diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeCustomFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeCustomFormatter.php
index f70160f..2be820b 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeCustomFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeCustomFormatter.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\datetime\Plugin\Field\FieldFormatter;
 
-use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\datetime\Plugin\Field\FieldType\DateRangeItem;
@@ -21,7 +20,7 @@
  *   }
  * )
  */
-class DateRangeCustomFormatter extends DateRangeFormatterBase {
+class DateRangeCustomFormatter extends DateTimeCustomFormatter {
 
   /**
    * {@inheritdoc}
@@ -29,6 +28,7 @@ class DateRangeCustomFormatter extends DateRangeFormatterBase {
   public static function defaultSettings() {
     return [
       'date_format' => DATETIME_DATETIME_STORAGE_FORMAT,
+      'separator' => '-',
     ] + parent::defaultSettings();
   }
 
@@ -40,38 +40,23 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
     $separator = $this->getSetting('separator');
 
     foreach ($items as $delta => $item) {
-      if ($item->start_date && $item->end_date) {
+      if (!empty($item->start_date) && !empty($item->end_date)) {
         /** @var \Drupal\Core\Datetime\DrupalDateTime $start_date */
         $start_date = $item->start_date;
         /** @var \Drupal\Core\Datetime\DrupalDateTime $end_date */
         $end_date = $item->end_date;
 
-        if ($this->getFieldSetting('datetime_type') == DateRangeItem::DATETIME_TYPE_DATE) {
-          // A date without time will pick up the current time, use the default.
-          datetime_date_default_time($start_date);
-          datetime_date_default_time($end_date);
-        }
-
-        $this->setTimeZone($start_date);
-        $this->setTimeZone($end_date);
-
-        $start = $this->formatDate($start_date);
-        $end = $this->formatDate($end_date);
-        if ($start !== $end) {
-          $output = $this->formatDate($start_date) . ' ' . $separator . ' ' . $this->formatDate($end_date);
+        if ($start_date->format('U') !== $end_date->format('U')) {
+          $elements[$delta] = [
+            $this->buildDate($start_date),
+            ['#plain_text' => ' ' . $separator . ' '],
+            $this->buildDate($end_date),
+            $this->defaultCacheContext(),
+          ];
         }
         else {
-          $output = $start;
+          $elements[$delta] = $this->buildDate($start_date) + $this->defaultCacheContext();
         }
-
-        $elements[$delta] = [
-          '#cache' => [
-            'contexts' => [
-              'timezone',
-            ],
-          ],
-          '#plain_text' => $output,
-        ];
       }
     }
 
@@ -81,23 +66,14 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
   /**
    * {@inheritdoc}
    */
-  protected function formatDate(DrupalDateTime $date) {
-    $format = $this->getSetting('date_format');
-    $timezone = $this->getSetting('timezone_override') ?: $date->getTimezone()->getName();
-    return $this->dateFormatter->format($date->getTimestamp(), 'custom', $format, $timezone != '' ? $timezone : NULL);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function settingsForm(array $form, FormStateInterface $form_state) {
     $form = parent::settingsForm($form, $form_state);
 
-    $form['date_format'] = [
+    $form['separator'] = [
       '#type' => 'textfield',
-      '#title' => $this->t('Date/time format'),
-      '#description' => $this->t('See <a href="http://php.net/manual/function.date.php" target="_blank">the documentation for PHP date formats</a>.'),
-      '#default_value' => $this->getSetting('date_format'),
+      '#title' => $this->t('Date separator'),
+      '#description' => $this->t('The string to separate the start and end dates'),
+      '#default_value' => $this->getSetting('separator'),
     ];
 
     return $form;
@@ -109,9 +85,9 @@ public function settingsForm(array $form, FormStateInterface $form_state) {
   public function settingsSummary() {
     $summary = parent::settingsSummary();
 
-    $date = DrupalDateTime::createFromTimestamp($this->requestStack->getCurrentRequest()->server->get('REQUEST_TIME'));
-    $this->setTimeZone($date);
-    $summary[] = $this->t('Format: @display', ['@display' => $this->formatDate($date)]);
+    if ($separator = $this->getSetting('separator')) {
+      $summary[] = $this->t('Separator: %separator', ['%separator' => $separator]);
+    }
 
     return $summary;
   }
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeDefaultFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeDefaultFormatter.php
index 1ee4ef8..2655315 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeDefaultFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeDefaultFormatter.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\datetime\Plugin\Field\FieldFormatter;
 
-use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\datetime\Plugin\Field\FieldType\DateRangeItem;
@@ -22,7 +21,7 @@
  *   }
  * )
  */
-class DateRangeDefaultFormatter extends DateRangeFormatterBase {
+class DateRangeDefaultFormatter extends DateTimeDefaultFormatter {
 
   /**
    * {@inheritdoc}
@@ -30,6 +29,7 @@ class DateRangeDefaultFormatter extends DateRangeFormatterBase {
   public static function defaultSettings() {
     return [
       'format_type' => 'medium',
+      'separator' => '-',
     ] + parent::defaultSettings();
   }
 
@@ -41,65 +41,22 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
     $separator = $this->getSetting('separator');
 
     foreach ($items as $delta => $item) {
-      if ($item->start_date && $item->end_date) {
+      if (!empty($item->start_date) && !empty($item->end_date)) {
         /** @var \Drupal\Core\Datetime\DrupalDateTime $start_date */
         $start_date = $item->start_date;
         /** @var \Drupal\Core\Datetime\DrupalDateTime $end_date */
         $end_date = $item->end_date;
 
-        if ($this->getFieldSetting('datetime_type') == DateRangeItem::DATETIME_TYPE_DATE) {
-          // A date without time will pick up the current time, use the default.
-          datetime_date_default_time($start_date);
-          datetime_date_default_time($end_date);
-        }
-
-        // Create the ISO dates in Universal Time.
-        $start_iso_date = $start_date->format("Y-m-d\TH:i:s") . 'Z';
-        $end_iso_date = $end_date->format("Y-m-d\TH:i:s") . 'Z';
-
-        $this->setTimeZone($start_date);
-        $this->setTimeZone($end_date);
-
-        // Display the dates using theme datetime.
-        $elements[$delta] = [
-          '#cache' => [
-            'contexts' => [
-              'timezone',
-            ],
-          ],
-        ];
-
-        $start = $this->formatDate($start_date);
-        $end = $this->formatDate($end_date);
-
-        if ($start !== $end) {
-          $elements[$delta][] = [
-            '#theme' => 'time',
-            '#text' => $start,
-            '#html' => FALSE,
-            '#attributes' => [
-              'datetime' => $start_iso_date,
-            ]
-          ];
-          $elements[$delta][] = ['#plain_text' => ' ' . $separator . ' '];
-          $elements[$delta][] = [
-            '#theme' => 'time',
-            '#text' => $end,
-            '#html' => FALSE,
-            '#attributes' => [
-              'datetime' => $end_iso_date,
-            ]
+        if ($start_date->format('U') !== $end_date->format('U')) {
+          $elements[$delta] = [
+            $this->buildDate($start_date),
+            ['#plain_text' => ' ' . $separator . ' '],
+            $this->buildDate($end_date),
+            $this->defaultCacheContext(),
           ];
         }
         else {
-          $elements[$delta][] = [
-            '#theme' => 'time',
-            '#text' => $start,
-            '#html' => FALSE,
-            '#attributes' => [
-              'datetime' => $start_iso_date,
-            ]
-          ];
+          $elements[$delta] = $this->buildDate($start_date) + $this->defaultCacheContext();
         }
 
         if (!empty($item->_attributes)) {
@@ -117,32 +74,14 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
   /**
    * {@inheritdoc}
    */
-  protected function formatDate(DrupalDateTime $date) {
-    $format_type = $this->getSetting('format_type');
-    $timezone = $this->getSetting('timezone_override') ?: $date->getTimezone()->getName();
-    return $this->dateFormatter->format($date->getTimestamp(), $format_type, '', $timezone != '' ? $timezone : NULL);
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function settingsForm(array $form, FormStateInterface $form_state) {
     $form = parent::settingsForm($form, $form_state);
 
-    $format_types = $this->dateFormatStorage->loadMultiple();
-    $options = [];
-
-    foreach ($format_types as $type => $type_info) {
-      $format = $this->dateFormatter->format(REQUEST_TIME, $type);
-      $options[$type] = $type_info->label() . ' (' . $format . ')';
-    }
-
-    $form['format_type'] = [
-      '#type' => 'select',
-      '#title' => $this->t('Date format'),
-      '#description' => $this->t('Choose a format for displaying the dates. Be sure to set a format appropriate for the field, i.e. omitting time for a field that only has a date.'),
-      '#options' => $options,
-      '#default_value' => $this->getSetting('format_type'),
+    $form['separator'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Date separator'),
+      '#description' => $this->t('The string to separate the start and end dates'),
+      '#default_value' => $this->getSetting('separator'),
     ];
 
     return $form;
@@ -154,9 +93,9 @@ public function settingsForm(array $form, FormStateInterface $form_state) {
   public function settingsSummary() {
     $summary = parent::settingsSummary();
 
-    $date = DrupalDateTime::createFromTimestamp($this->requestStack->getCurrentRequest()->server->get('REQUEST_TIME'));
-    $this->setTimeZone($date);
-    $summary[] = $this->t('Format: @display', ['@display' => $this->formatDate($date)]);
+    if ($separator = $this->getSetting('separator')) {
+      $summary[] = $this->t('Separator: %separator', ['%separator' => $separator]);
+    }
 
     return $summary;
   }
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeFormatterBase.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeFormatterBase.php
deleted file mode 100644
index f0c40d4..0000000
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangeFormatterBase.php
+++ /dev/null
@@ -1,194 +0,0 @@
-<?php
-
-namespace Drupal\datetime\Plugin\Field\FieldFormatter;
-
-use Drupal\Core\Datetime\DateFormatterInterface;
-use Drupal\Core\Datetime\DrupalDateTime;
-use Drupal\Core\Entity\EntityStorageInterface;
-use Drupal\Core\Field\FieldDefinitionInterface;
-use Drupal\Core\Field\FormatterBase;
-use Drupal\Core\Form\FormStateInterface;
-use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
-use Drupal\datetime\Plugin\Field\FieldType\DateRangeItem;
-use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\HttpFoundation\RequestStack;
-
-
-/**
- * Base class for 'DateRange Field formatter' plugin implementations.
- */
-abstract class DateRangeFormatterBase extends FormatterBase implements ContainerFactoryPluginInterface {
-
-  /**
-   * The date formatter service.
-   *
-   * @var \Drupal\Core\Datetime\DateFormatterInterface
-   */
-  protected $dateFormatter;
-
-  /**
-   * The date format entity storage.
-   *
-   * @var \Drupal\Core\Entity\EntityStorageInterface
-   */
-  protected $dateFormatStorage;
-
-  /**
-   * The request stack.
-   *
-   * @var \Symfony\Component\HttpFoundation\RequestStack
-   */
-  protected $requestStack;
-
-  /**
-   * Constructs a new object which extends DateRangeFormatterBase.
-   *
-   * @param string $plugin_id
-   *   The plugin_id for the formatter.
-   * @param mixed $plugin_definition
-   *   The plugin implementation definition.
-   * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
-   *   The definition of the field to which the formatter is associated.
-   * @param array $settings
-   *   The formatter settings.
-   * @param string $label
-   *   The formatter label display setting.
-   * @param string $view_mode
-   *   The view mode.
-   * @param array $third_party_settings
-   *   Third party settings.
-   * @param \Drupal\Core\Datetime\DateFormatterInterface $date_formatter
-   *   The date formatter service.
-   * @param \Drupal\Core\Entity\EntityStorageInterface $date_format_storage
-   *   The date format entity storage.
-   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
-   *   The request stack used to retrieve the current request.
-   */
-  public function __construct($plugin_id, $plugin_definition, FieldDefinitionInterface $field_definition, array $settings, $label, $view_mode, array $third_party_settings, DateFormatterInterface $date_formatter, EntityStorageInterface $date_format_storage, RequestStack $request_stack) {
-    parent::__construct($plugin_id, $plugin_definition, $field_definition, $settings, $label, $view_mode, $third_party_settings);
-
-    $this->dateFormatter = $date_formatter;
-    $this->dateFormatStorage = $date_format_storage;
-    $this->requestStack = $request_stack;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
-    return new static(
-      $plugin_id,
-      $plugin_definition,
-      $configuration['field_definition'],
-      $configuration['settings'],
-      $configuration['label'],
-      $configuration['view_mode'],
-      $configuration['third_party_settings'],
-      $container->get('date.formatter'),
-      $container->get('entity_type.manager')->getStorage('date_format'),
-      $container->get('request_stack')
-    );
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function defaultSettings() {
-    return [
-      'separator' => '-',
-      'timezone_override' => '',
-    ] + parent::defaultSettings();
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function settingsForm(array $form, FormStateInterface $form_state) {
-    $form = parent::settingsForm($form, $form_state);
-
-    $form['separator'] = [
-      '#type' => 'textfield',
-      '#title' => $this->t('Date separator'),
-      '#description' => $this->t('The string to separate the start and end dates'),
-      '#default_value' => $this->getSetting('separator'),
-    ];
-
-    $form['timezone_override'] = [
-      '#type' => 'select',
-      '#title' => $this->t('Time zone override'),
-      '#description' => $this->t('The time zone selected here will always be used'),
-      '#options' => system_time_zones(TRUE),
-      '#default_value' => $this->getSetting('timezone_override'),
-    ];
-
-    return $form;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function settingsSummary() {
-    $summary = parent::settingsSummary();
-
-    if ($separator = $this->getSetting('separator')) {
-      $summary[] = $this->t('Separator: %separator', ['%separator' => $separator]);
-    }
-
-    if ($override = $this->getSetting('timezone_override')) {
-      $summary[] = $this->t('Time zone: @timezone', ['@timezone' => $override]);
-    }
-
-    return $summary;
-  }
-
-  /**
-   * Creates a formatted date as a string.
-   *
-   * @param \Drupal\Core\Datetime\DrupalDateTime $date
-   *   The date.
-   *
-   * @return string
-   *   A formatted date range string using the chosen format.
-   */
-  abstract protected function formatDate(DrupalDateTime $date);
-
-  /**
-   * Sets the proper time zone on a DrupalDateTime object for the current user.
-   *
-   * A DrupalDateTime object loaded from the database will have the UTC time
-   * zone applied to it.  This method will apply the time zone for the current
-   * user, based on system and user settings.
-   *
-   * @see drupal_get_user_timezone()
-   *
-   * @param \Drupal\Core\Datetime\DrupalDateTime $date
-   *   A DrupalDateTime object.
-   */
-  protected function setTimeZone(DrupalDateTime $date) {
-    if ($this->getFieldSetting('datetime_type') === DateRangeItem::DATETIME_TYPE_DATE) {
-      // A date without time has no timezone conversion.
-      $timezone = DATETIME_STORAGE_TIMEZONE;
-    }
-    else {
-      $timezone = drupal_get_user_timezone();
-    }
-    $date->setTimeZone(timezone_open($timezone));
-  }
-
-  /**
-   * Gets a settings array suitable for DrupalDateTime::format().
-   *
-   * @return array
-   *   The settings array that can be passed to DrupalDateTime::format().
-   */
-  protected function getFormatSettings() {
-    $settings = [];
-
-    if ($this->getSetting('timezone_override') != '') {
-      $settings['timezone'] = $this->getSetting('timezone_override');
-    }
-
-    return $settings;
-  }
-
-}
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangePlainFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangePlainFormatter.php
index 06c24ac..e110c4d 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangePlainFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateRangePlainFormatter.php
@@ -2,8 +2,8 @@
 
 namespace Drupal\datetime\Plugin\Field\FieldFormatter;
 
-use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Form\FormStateInterface;
 use Drupal\datetime\Plugin\Field\FieldType\DateRangeItem;
 
 /**
@@ -20,7 +20,16 @@
  *   }
  * )
  */
-class DateRangePlainFormatter extends DateRangeFormatterBase {
+class DateRangePlainFormatter extends DateTimePlainFormatter {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'separator' => '-',
+    ] + parent::defaultSettings();
+  }
 
   /**
    * {@inheritdoc}
@@ -30,38 +39,23 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
     $separator = $this->getSetting('separator');
 
     foreach ($items as $delta => $item) {
-      if ($item->start_date && $item->end_date) {
+      if (!empty($item->start_date) && !empty($item->end_date)) {
         /** @var \Drupal\Core\Datetime\DrupalDateTime $start_date */
         $start_date = $item->start_date;
         /** @var \Drupal\Core\Datetime\DrupalDateTime $end_date */
         $end_date = $item->end_date;
 
-        if ($this->getFieldSetting('datetime_type') == DateRangeItem::DATETIME_TYPE_DATE) {
-          // A date without time will pick up the current time, use the default.
-          datetime_date_default_time($start_date);
-          datetime_date_default_time($end_date);
-        }
-
-        $this->setTimeZone($start_date);
-        $this->setTimeZone($end_date);
-
-        $start = $this->formatDate($start_date);
-        $end = $this->formatDate($end_date);
-        if ($start !== $end) {
-          $output = $this->formatDate($start_date) . ' ' . $separator . ' ' . $this->formatDate($end_date);
+        if ($start_date->format('U') !== $end_date->format('U')) {
+          $elements[$delta] = [
+            $this->buildDate($start_date),
+            ['#plain_text' => ' ' . $separator . ' '],
+            $this->buildDate($end_date),
+            $this->defaultCacheContext(),
+          ];
         }
         else {
-          $output = $start;
+          $elements[$delta] = $this->buildDate($start_date) + $this->defaultCacheContext();
         }
-
-        $elements[$delta] = [
-          '#cache' => [
-            'contexts' => [
-              'timezone',
-            ],
-          ],
-          '#plain_text' => $output,
-        ];
       }
     }
 
@@ -71,10 +65,30 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
   /**
    * {@inheritdoc}
    */
-  protected function formatDate(DrupalDateTime $date) {
-    $format = $this->getFieldSetting('datetime_type') == DateRangeItem::DATETIME_TYPE_DATE ? DATETIME_DATE_STORAGE_FORMAT : DATETIME_DATETIME_STORAGE_FORMAT;
-    $timezone = $this->getSetting('timezone_override') ?: $date->getTimezone()->getName();
-    return $this->dateFormatter->format($date->getTimestamp(), 'custom', $format, $timezone != '' ? $timezone : NULL);
+  public function settingsForm(array $form, FormStateInterface $form_state) {
+    $form = parent::settingsForm($form, $form_state);
+
+    $form['separator'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Date separator'),
+      '#description' => $this->t('The string to separate the start and end dates'),
+      '#default_value' => $this->getSetting('separator'),
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsSummary() {
+    $summary = parent::settingsSummary();
+
+    if ($separator = $this->getSetting('separator')) {
+      $summary[] = $this->t('Separator: %separator', ['%separator' => $separator]);
+    }
+
+    return $summary;
   }
 
 }
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php
index 678ddc8..f68bbe3 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeCustomFormatter.php
@@ -5,6 +5,7 @@
 use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;
 
 /**
  * Plugin implementation of the 'Custom' formatter for 'datetime' fields.
@@ -35,27 +36,10 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
     $elements = array();
 
     foreach ($items as $delta => $item) {
-      $output = '';
       if (!empty($item->date)) {
         /** @var \Drupal\Core\Datetime\DrupalDateTime $date */
-        $date = $item->date;
-
-        if ($this->getFieldSetting('datetime_type') == 'date') {
-          // A date without time will pick up the current time, use the default.
-          datetime_date_default_time($date);
-        }
-        $this->setTimeZone($date);
-
-        $output = $this->formatDate($date);
+        $elements[$delta] = $this->buildDate($item->date) + $this->defaultCacheContext();
       }
-      $elements[$delta] = [
-        '#markup' => $output,
-        '#cache' => [
-          'contexts' => [
-            'timezone',
-          ],
-        ],
-      ];
     }
 
     return $elements;
@@ -66,13 +50,30 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
    */
   protected function formatDate($date) {
     $format = $this->getSetting('date_format');
-    $timezone = $this->getSetting('timezone_override');
+    $timezone = $this->getSetting('timezone_override') ?: $date->getTimezone()->getName();
     return $this->dateFormatter->format($date->getTimestamp(), 'custom', $format, $timezone != '' ? $timezone : NULL);
   }
 
   /**
    * {@inheritdoc}
    */
+  protected function buildDate($date) {
+    if ($this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE) {
+      // A date without time will pick up the current time, use the default.
+      datetime_date_default_time($date);
+    }
+    $this->setTimeZone($date);
+
+    $build = [
+      '#plain_text' => $this->formatDate($date),
+    ];
+
+    return $build;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function settingsForm(array $form, FormStateInterface $form_state) {
     $form = parent::settingsForm($form, $form_state);
 
@@ -94,7 +95,7 @@ public function settingsSummary() {
 
     $date = new DrupalDateTime();
     $this->setTimeZone($date);
-    $summary[] = $date->format($this->getSetting('date_format'), $this->getFormatSettings());
+    $summary[] = $this->t('Format: @display', ['@display' => $this->formatDate($date)]);
 
     return $summary;
   }
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
index 03c92ae..0d3d2e8 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeDefaultFormatter.php
@@ -5,6 +5,7 @@
 use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldItemListInterface;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\datetime\Plugin\Field\FieldType\DateTimeItem;
 
 /**
  * Plugin implementation of the 'Default' formatter for 'datetime' fields.
@@ -35,45 +36,17 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
     $elements = array();
 
     foreach ($items as $delta => $item) {
-      $output = '';
-      $iso_date = '';
-
-      if ($item->date) {
+      if (!empty($item->date)) {
         /** @var \Drupal\Core\Datetime\DrupalDateTime $date */
-        $date = $item->date;
-
-        if ($this->getFieldSetting('datetime_type') == 'date') {
-          // A date without time will pick up the current time, use the default.
-          datetime_date_default_time($date);
+        // Display the date using theme datetime.
+        $elements[$delta] = $this->buildDate($item->date) + $this->defaultCacheContext();
+
+        if (!empty($item->_attributes)) {
+          $elements[$delta]['#attributes'] += $item->_attributes;
+          // Unset field item attributes since they have been included in the
+          // formatter output and should not be rendered in the field template.
+          unset($item->_attributes);
         }
-
-        // Create the ISO date in Universal Time.
-        $iso_date = $date->format("Y-m-d\TH:i:s") . 'Z';
-
-        $this->setTimeZone($date);
-
-        $output = $this->formatDate($date);
-      }
-
-      // Display the date using theme datetime.
-      $elements[$delta] = array(
-        '#cache' => [
-          'contexts' => [
-            'timezone',
-          ],
-        ],
-        '#theme' => 'time',
-        '#text' => $output,
-        '#html' => FALSE,
-        '#attributes' => array(
-          'datetime' => $iso_date,
-        ),
-      );
-      if (!empty($item->_attributes)) {
-        $elements[$delta]['#attributes'] += $item->_attributes;
-        // Unset field item attributes since they have been included in the
-        // formatter output and should not be rendered in the field template.
-        unset($item->_attributes);
       }
     }
 
@@ -93,6 +66,32 @@ protected function formatDate($date) {
   /**
    * {@inheritdoc}
    */
+  protected function buildDate($date) {
+    if ($this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE) {
+      // A date without time will pick up the current time, use the default.
+      datetime_date_default_time($date);
+    }
+
+    // Create the ISO date in Universal Time.
+    $iso_date = $date->format("Y-m-d\TH:i:s") . 'Z';
+
+    $this->setTimeZone($date);
+
+    $build = [
+      '#theme' => 'time',
+      '#text' => $this->formatDate($date),
+      '#html' => FALSE,
+      '#attributes' => [
+        'datetime' => $iso_date,
+      ],
+    ];
+
+    return $build;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function settingsForm(array $form, FormStateInterface $form_state) {
     $form = parent::settingsForm($form, $form_state);
 
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
index be9df38..2546969 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimeFormatterBase.php
@@ -129,6 +129,47 @@ public function settingsSummary() {
   abstract protected function formatDate($date);
 
   /**
+   * Creates a render array from a data object.
+   *
+   * Note: the caller is responsible for setting the proper cache context, which
+   * is typically
+   * @code
+   * [
+   *   '#cache' => [
+   *     'contexts' => [
+   *       'timezone',
+   *     ],
+   *   ]
+   * ]
+   * @endcode
+   * This is to allow this method to be used multiple times to create a render
+   * array, without creating redundant cache contexts for each element.
+   *
+   * @param \Drupal\Core\Datetime\DrupalDateTime $date
+   *   A date object.
+   *
+   * @return array
+   *   A render array.
+   */
+  abstract protected function buildDate($date);
+
+  /**
+   * Returns the default cache context for the formatter.
+   *
+   * @return array
+   *   A render array.
+   */
+  protected function defaultCacheContext() {
+    return [
+      '#cache' => [
+        'contexts' => [
+          'timezone',
+        ],
+      ],
+    ];
+  }
+
+  /**
    * Sets the proper time zone on a DrupalDateTime object for the current user.
    *
    * A DrupalDateTime object loaded from the database will have the UTC time
diff --git a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php
index 683d75c..0ee0da7 100644
--- a/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php
+++ b/core/modules/datetime/src/Plugin/Field/FieldFormatter/DateTimePlainFormatter.php
@@ -25,27 +25,10 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
     $elements = array();
 
     foreach ($items as $delta => $item) {
-      $output = '';
       if (!empty($item->date)) {
         /** @var \Drupal\Core\Datetime\DrupalDateTime $date */
-        $date = $item->date;
-
-        if ($this->getFieldSetting('datetime_type') == 'date') {
-          // A date without time will pick up the current time, use the default.
-          datetime_date_default_time($date);
-        }
-        $this->setTimeZone($date);
-
-        $output = $this->formatDate($date);
+        $elements[$delta] = $this->buildDate($item->date) + $this->defaultCacheContext();
       }
-      $elements[$delta] = [
-        '#cache' => [
-          'contexts' => [
-            'timezone',
-          ],
-        ],
-        '#markup' => $output,
-      ];
     }
 
     return $elements;
@@ -56,8 +39,25 @@ public function viewElements(FieldItemListInterface $items, $langcode) {
    */
   protected function formatDate($date) {
     $format = $this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE ? DATETIME_DATE_STORAGE_FORMAT : DATETIME_DATETIME_STORAGE_FORMAT;
-    $timezone = $this->getSetting('timezone_override');
+    $timezone = $this->getSetting('timezone_override') ?: $date->getTimezone()->getName();
     return $this->dateFormatter->format($date->getTimestamp(), 'custom', $format, $timezone != '' ? $timezone : NULL);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function buildDate($date) {
+    if ($this->getFieldSetting('datetime_type') == DateTimeItem::DATETIME_TYPE_DATE) {
+      // A date without time will pick up the current time, use the default.
+      datetime_date_default_time($date);
+    }
+    $this->setTimeZone($date);
+
+    $build = [
+      '#plain_text' => $this->formatDate($date),
+    ];
+
+    return $build;
+  }
+
 }