diff --git a/core/lib/Drupal/Core/Datetime/Date.php b/core/lib/Drupal/Core/Datetime/Date.php
index 51a16eb..67d6519 100644
--- a/core/lib/Drupal/Core/Datetime/Date.php
+++ b/core/lib/Drupal/Core/Datetime/Date.php
@@ -136,15 +136,16 @@ public function format($timestamp, $type = 'medium', $format = '', $timezone = N
    * @return string The pattern for the date format in the given language.
    */
   protected function dateFormat($format, $langcode = NULL) {
+    // If a langcode is not given, we use the interface language.
     $needs_language_context = !empty($langcode);
-    if (empty($langcode)) {
+    if (!$needs_language_context) {
       $langcode = $this->languageManager->getLanguage(Language::TYPE_INTERFACE)->id;
     }
     if (!isset($this->dateFormats[$format][$langcode])) {
       // Enter a language specific context for the language if some language is
       // given, so the right date format is loaded.
       $needs_language_context = $needs_language_context &&
-          \Drupal::moduleHandler()->moduleExists('language') && !empty($langcode);
+          \Drupal::moduleHandler()->moduleExists('language');
       if ($needs_language_context) {
         $language_context = config_context_enter('Drupal\language\LanguageConfigContext');
         $language_context->setLanguage(new Language(array('id' => $langcode)));
diff --git a/core/modules/system/config/schema/system.data_types.schema.yml b/core/modules/system/config/schema/system.data_types.schema.yml
index 8688762..ab375b6 100644
--- a/core/modules/system/config/schema/system.data_types.schema.yml
+++ b/core/modules/system/config/schema/system.data_types.schema.yml
@@ -53,7 +53,7 @@ text:
   label: 'Text'
   translatable: true
 
-# PHP Date format string that is translatable and has a specific UI.
+# PHP Date format string that is translatable.
 date_format:
   type: string
   label: 'PHP date format'