diff --git a/core/lib/Drupal/Core/Datetime/DateFormatter.php b/core/lib/Drupal/Core/Datetime/DateFormatter.php
index 0b4f817..6bbd77f 100644
--- a/core/lib/Drupal/Core/Datetime/DateFormatter.php
+++ b/core/lib/Drupal/Core/Datetime/DateFormatter.php
@@ -193,6 +193,33 @@ public function formatInterval($interval, $granularity = 2, $langcode = NULL) {
   }
 
   /**
+   * Provides all date format characters value for given timestamp.
+   *
+   * @param string|null $langcode
+   *   Language code of date format.
+   * @param int|null $timestamp
+   *   Unix timestamp.
+   * @param string|null $timezone
+   *   String timezone.
+   *
+   * @return array
+   *   An array of formatted date value indexed by date character.
+   */
+  public function getSampleDateFormats($langcode = NULL, $timestamp = NULL, $timezone = NULL) {
+    $language_code = $langcode ?: NULL;
+    $ts = $timestamp ?: REQUEST_TIME;
+    $tz = $timezone ?: NULL;
+    // All date format characters in PHP.
+    $date_characters = 'dDjlNSwzWFmMntLoYyaABgGhHisueIOPTZcrU';
+    $date_chars = str_split($date_characters);
+    $date_elements = array_combine($date_chars, $date_chars);
+    array_walk($date_elements, function(&$character) use ($ts, $tz, $language_code) {
+      $character = $this->format($ts, 'custom', $character, $tz, $language_code);
+    });
+    return $date_elements;
+  }
+
+  /**
    * Loads the given format pattern for the given langcode.
    *
    * @param string $format
diff --git a/core/modules/config_translation/src/FormElement/DateFormat.php b/core/modules/config_translation/src/FormElement/DateFormat.php
index ea947af..f833362 100644
--- a/core/modules/config_translation/src/FormElement/DateFormat.php
+++ b/core/modules/config_translation/src/FormElement/DateFormat.php
@@ -22,8 +22,10 @@ class DateFormat extends FormElementBase {
    * {@inheritdoc}
    */
   public function getTranslationElement(LanguageInterface $translation_language, $source_config, $translation_config) {
+    /** @var \Drupal\Core\Datetime\DateFormatter $date_formatter */
+    $date_formatter = \Drupal::service('date.formatter');
     $description = $this->t('A user-defined date format. See the <a href="@url">PHP manual</a> for available options.', array('@url' => 'http://php.net/manual/function.date.php'));
-    $format = $this->t('Displayed as %date_format', array('%date_format' => \Drupal::service('date.formatter')->format(REQUEST_TIME, 'custom', $translation_config)));
+    $format = $this->t('Displayed as %date_format', array('%date_format' => $date_formatter->format(REQUEST_TIME, 'custom', $translation_config)));
 
     return array(
       '#type' => 'textfield',
@@ -33,7 +35,7 @@ public function getTranslationElement(LanguageInterface $translation_language, $
         'class' => array('date-formatter'),
       ),
       '#attached' => array(
-        'drupalSettings' => array('dateFormats' => $this->getSampleDateFormats($translation_language->getId())),
+        'drupalSettings' => array('dateFormats' => $date_formatter->getSampleDateFormats($translation_language->getId())),
       ),
 
     ) + parent::getTranslationElement($translation_language, $source_config, $translation_config);
@@ -50,26 +52,4 @@ public function getFormAttributes() {
     );
   }
 
-  /**
-   * Provides all date format characters for date format preview on client side.
-   *
-   * @param int|null $timestamp
-   * @return array
-   *   An array of date character values keyed by characters.
-   */
-  protected function getSampleDateFormats($langcode, $timestamp = NULL, $timezone = NULL) {
-    $tz = $timezone ?: date_default_timezone_get();
-    $ts = $timestamp ?: REQUEST_TIME;
-    // All date format characters in PHP.
-    $date_characters = 'dDjlNSwzWFmMntLoYyaABgGhHisueIOPTZcrU';
-    $date_chars = str_split($date_characters);
-    $date_elements = array_combine($date_chars, $date_chars);
-    /** @var \Drupal\Core\Datetime\DateFormatter $date_formatter */
-    $date_formatter = \Drupal::service('date.formatter');
-    array_walk($date_elements, function(&$character) use ($ts, $date_formatter, $langcode, $tz) {
-      $character = $date_formatter->format($ts, 'custom', $character, $tz, $langcode);
-    });
-    return $date_elements;
-  }
-
 }
diff --git a/core/modules/config_translation/src/FormElement/ElementInterface.php b/core/modules/config_translation/src/FormElement/ElementInterface.php
index 22ab0ef..c9fb0b9 100644
--- a/core/modules/config_translation/src/FormElement/ElementInterface.php
+++ b/core/modules/config_translation/src/FormElement/ElementInterface.php
@@ -70,11 +70,11 @@ public function getTranslationBuild(LanguageInterface $source_language, Language
    */
   public function setConfig(Config $base_config, LanguageConfigOverride $config_translation, $config_values, $base_key = NULL);
 
-
   /**
-   * Builds a form attributes for the configuration form.
+   * Allows to provide form attributes for the configuration form.
    *
-   * @return mixed
+   * @return array
+   *   An array of form attributes.
    */
   public function getFormAttributes();
 
diff --git a/core/modules/config_translation/src/FormElement/FormElementBase.php b/core/modules/config_translation/src/FormElement/FormElementBase.php
index b8438d7..53cf5ff 100644
--- a/core/modules/config_translation/src/FormElement/FormElementBase.php
+++ b/core/modules/config_translation/src/FormElement/FormElementBase.php
@@ -74,6 +74,9 @@ public function getTranslationBuild(LanguageInterface $source_language, Language
     return $build;
   }
 
+  /**
+   * {@inheritdoc}
+   */
   public function getFormAttributes() {
     return array();
   }
diff --git a/core/modules/system/src/Form/DateFormatFormBase.php b/core/modules/system/src/Form/DateFormatFormBase.php
index 0c46500..c2c86ab 100644
--- a/core/modules/system/src/Form/DateFormatFormBase.php
+++ b/core/modules/system/src/Form/DateFormatFormBase.php
@@ -120,7 +120,7 @@ public function form(array $form, FormStateInterface $form_state) {
       '#languages' => LanguageInterface::STATE_ALL,
       '#default_value' => $this->entity->language()->getId(),
     );
-    $form['#attached']['drupalSettings']['dateFormats'] = $this->getSampleDateFormats();
+    $form['#attached']['drupalSettings']['dateFormats'] = $this->dateFormatter->getSampleDateFormats();
     $form['#attached']['library'][] = 'system/drupal.system.date';
     return parent::form($form, $form_state);
   }
@@ -165,23 +165,4 @@ public function save(array $form, FormStateInterface $form_state) {
     $form_state->setRedirectUrl($this->entity->urlInfo('collection'));
   }
 
-  /**
-   * Provides all date format characters for date format preview on client side.
-   *
-   * @param int|null $timestamp
-   * @return array
-   *   An array of date character values keyed by characters.
-   */
-  protected function getSampleDateFormats($timestamp = NULL) {
-    $ts = $timestamp ?: REQUEST_TIME;
-    // All date format characters in PHP.
-    $date_characters = 'dDjlNSwzWFmMntLoYyaABgGhHisueIOPTZcrU';
-    $date_chars = str_split($date_characters);
-    $date_elements = array_combine($date_chars, $date_chars);
-    array_walk($date_elements, function(&$character) use ($ts) {
-      $character = $this->dateFormatter->format($ts, 'custom', $character);
-    });
-    return $date_elements;
-  }
-
 }