diff --git a/core/modules/locale/locale.install b/core/modules/locale/locale.install
index af08d52..c527cca 100644
--- a/core/modules/locale/locale.install
+++ b/core/modules/locale/locale.install
@@ -944,22 +944,14 @@ function locale_update_8015() {
  * Converts localized date formats.
  */
 function locale_update_8016() {
-  $configs = array();
-
   // Fetch all date types from {date_format_type}.
   $result = db_query('SELECT * FROM {date_format_locale}');
   foreach ($result as $format) {
     $language = $format->language;
     // Create config objects for the language if not yet done.
-    if (!isset($configs[$language])) {
-      $configs[$language] = config('locale.config.' . $language . '.system.date');
-    }
-    $configs[$language]->set('formats.' . $format->type . '.pattern.php', $format->format);
-  }
-
-  // Save all instantiated config objects.
-  foreach ($configs as $config) {
-    $config->save();
+    config("locale.config.$language.system.date_format." . $format->type)
+      ->set('pattern.php', $format->format)
+      ->save();
   }
 }
 
diff --git a/core/modules/system/lib/Drupal/system/DateFormatInterface.php b/core/modules/system/lib/Drupal/system/DateFormatInterface.php
index fc53d8d..ae35fae 100644
--- a/core/modules/system/lib/Drupal/system/DateFormatInterface.php
+++ b/core/modules/system/lib/Drupal/system/DateFormatInterface.php
@@ -49,4 +49,9 @@ public function setLocales(array $locales);
    */
   public function getLocales();
 
+  /**
+   * @return bool
+   */
+  public function hasLocales();
+
 }
diff --git a/core/modules/system/lib/Drupal/system/Form/DateFormatLocalizeResetForm.php b/core/modules/system/lib/Drupal/system/Form/DateFormatLocalizeResetForm.php
index a3576c5..cb58c3f 100644
--- a/core/modules/system/lib/Drupal/system/Form/DateFormatLocalizeResetForm.php
+++ b/core/modules/system/lib/Drupal/system/Form/DateFormatLocalizeResetForm.php
@@ -101,7 +101,9 @@ public function buildForm(array $form, array &$form_state, $langcode = NULL) {
    * {@inheritdoc}
    */
   public function submitForm(array &$form, array &$form_state) {
-    $this->configFactory->get('locale.config.' . $this->language->langcode . '.system.date')->delete();
+    foreach (config_get_storage_names_with_prefix('locale.config.' . $this->language->langcode . '.system.date_format') as $config_id) {
+      $this->configFactory->get($config_id)->delete();
+    }
 
     $form_state['redirect'] = 'admin/config/regional/date-time/locale';
   }
diff --git a/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/DateFormat.php b/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/DateFormat.php
index 2f30fae..7cb8a3f 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/DateFormat.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/Core/Entity/DateFormat.php
@@ -140,6 +140,13 @@ public function setLocales(array $locales) {
   /**
    * {@inheritdoc}
    */
+  public function hasLocales() {
+    return !empty($this->locales);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function addLocale($locale) {
     $this->locales[] = $locale;
     $this->locales = array_unique($this->locales);
diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/DateUpgradePathTest.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/DateUpgradePathTest.php
index ce48a3d..990cbd5 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/DateUpgradePathTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/DateUpgradePathTest.php
@@ -91,10 +91,10 @@ public function testDateUpgrade() {
       ),
     );
 
-    $config = config('locale.config.de.system.date');
     foreach ($expected_de_formats as $locale_format) {
-      $format = $config->get('formats.' . $locale_format['type'] . '.pattern.php');
+      $format = config('locale.config.de.system.date_format.' . $locale_format['type'])->get('pattern.php');
       $this->assertEqual($locale_format['format'], $format);
     }
   }
+
 }
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index c55b0f6..4dd7e5e 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -5,6 +5,7 @@
  * Admin page callbacks for the system module.
  */
 
+use Drupal\system\DateFormatInterface;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 use Drupal\system\Form\ModulesInstallConfirmForm;
@@ -1824,21 +1825,16 @@ function system_date_format_localize_form($form, &$form_state, $langcode) {
   $choices = array();
   foreach ($formats as $date_format_id => $format_info) {
     // Ignore values that are localized.
-    if (empty($format_info->locales)) {
+    if (!$format_info->hasLocales()) {
       $choices[$date_format_id] = format_date(REQUEST_TIME, $date_format_id);
     }
-    else {
-      unset($formats[$date_format_id]);
-    }
   }
 
   // Get configured formats for each language.
-  $locale_formats = system_date_format_locale($langcode);
-  if (!empty($locale_formats)) {
-    $formats += $locale_formats;
-    foreach ($locale_formats as $date_format_id => $format_info) {
-      $choices[$date_format_id] = format_date(REQUEST_TIME, $date_format_id);
-    }
+  $config_prefix = 'locale.config.' . $langcode . '.system.date_format';
+  foreach (config_get_storage_names_with_prefix($config_prefix) as $config_id) {
+    $date_format_id = substr($config_id, strlen($config_prefix. '.'));
+    $choices[$date_format_id] = format_date(REQUEST_TIME, $date_format_id);
   }
 
   // Display a form field for each format type.
@@ -1872,7 +1868,7 @@ function system_date_format_localize_form_submit($form, &$form_state) {
   foreach ($formats as $date_format_id => $format_info) {
     if (isset($form_state['values']['date_format_' . $date_format_id])) {
       $format = $form_state['values']['date_format_' . $date_format_id];
-      system_date_format_localize_form_save($langcode, $date_format_id, $formats[$format]->get('pattern'));
+      system_date_format_localize_form_save($langcode, $format_info, $formats[$format]->get('pattern'));
     }
   }
   drupal_set_message(t('Configuration saved.'));
@@ -1913,16 +1909,17 @@ function theme_system_date_format_localize_form($variables) {
 /**
  * Save locale specific date formats to the database.
  *
- * @param $langcode
+ * @param string $langcode
  *   Language code, can be 2 characters, e.g. 'en' or 5 characters, e.g.
  *   'en-CA'.
- * @param $date_format_id
- *   Date format id, e.g. 'short', 'medium'.
- * @param $format
+ * @param \Drupal\system\DateFormatInterface $date_format
+ *   The date format entity.
+ * @param string $format
  *   The date format string.
  */
-function system_date_format_localize_form_save($langcode, $date_format_id, $format) {
-  config('locale.config.' . $langcode . '.system.date')
-    ->set('formats.' . $date_format_id . '.pattern', $format)
+function system_date_format_localize_form_save($langcode, DateFormatInterface $date_format, $format) {
+  $date_format->addLocale($langcode)->save();
+  config('locale.config.' . $langcode . '.system.date_format.' . $date_format->id())
+    ->set('pattern', $format)
     ->save();
 }
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index f457656..9b2be4c 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -3656,39 +3656,6 @@ function system_run_automated_cron() {
 }
 
 /**
- * Gets the appropriate date format string for a date type and locale.
- *
- * @param $langcode
- *   (optional) String language code for the current locale. This can be a 2 character
- *   language code like 'en' and 'fr' or a 5 character language code like
- *   'en-gb' and 'en-us'.
- * @param $date_format_id
- *   (optional) String machine name for the date format.
- *
- * @return
- *   If $date_format_id and $langcode are specified, returns the corresponding
- *   date format string. If only $langcode is specified, returns an array of
- *   all date format strings for that locale, keyed by the date type. If
- *   neither is specified returns FALSE.
- */
-function system_date_format_locale($langcode = NULL, $date_format_id = NULL) {
-  $formats = &drupal_static(__FUNCTION__);
-
-  if (!isset($formats[$langcode])) {
-    $formats[$langcode] = config('locale.config.' . $langcode . '.system.date')->get('formats');
-  }
-
-  if ($date_format_id && $langcode && !empty($formats[$langcode][$date_format_id])) {
-    return $formats[$langcode][$date_format_id];
-  }
-  elseif ($langcode && !empty($formats[$langcode])) {
-    return $formats[$langcode];
-  }
-
-  return FALSE;
-}
-
-/**
  * Returns HTML for a confirmation form.
  *
  * By default this does not alter the appearance of a form at all,