diff --git a/core/lib/Drupal/Core/Datetime/DateFormatter.php b/core/lib/Drupal/Core/Datetime/DateFormatter.php
index 35987b7..9aadb05 100644
--- a/core/lib/Drupal/Core/Datetime/DateFormatter.php
+++ b/core/lib/Drupal/Core/Datetime/DateFormatter.php
@@ -260,7 +260,7 @@ protected function country() {
   /**
    * Setter for country.
    *
-   * @param $country_code
+   * @param string $country_code
    */
   public function setCountry($country_code) {
     $this->country = $country_code;
diff --git a/core/modules/config_translation/src/FormElement/FormElementBase.php b/core/modules/config_translation/src/FormElement/FormElementBase.php
index 53cf5ff..1ee5e77 100644
--- a/core/modules/config_translation/src/FormElement/FormElementBase.php
+++ b/core/modules/config_translation/src/FormElement/FormElementBase.php
@@ -78,7 +78,7 @@ public function getTranslationBuild(LanguageInterface $source_language, Language
    * {@inheritdoc}
    */
   public function getFormAttributes() {
-    return array();
+    return [];
   }
 
   /**
diff --git a/core/modules/config_translation/src/FormElement/ListElement.php b/core/modules/config_translation/src/FormElement/ListElement.php
index 3a0c138..4723203 100644
--- a/core/modules/config_translation/src/FormElement/ListElement.php
+++ b/core/modules/config_translation/src/FormElement/ListElement.php
@@ -100,7 +100,7 @@ public function setConfig(Config $base_config, LanguageConfigOverride $config_tr
    * {@inheritdoc}
    */
   public function getFormAttributes() {
-    $attributes = array();
+    $attributes = [];
     foreach ($this->element as $key => $element) {
       if ($form_element = ConfigTranslationFormBase::createFormElement($element)) {
         $form_attributes = $form_element->getFormAttributes();
diff --git a/core/modules/system/js/system.date.js b/core/modules/system/js/system.date.js
index fcab3ef..4f34a7b 100644
--- a/core/modules/system/js/system.date.js
+++ b/core/modules/system/js/system.date.js
@@ -9,10 +9,10 @@
    */
   Drupal.behaviors.dateFormat = {
     attach: function (context) {
-      var $context = $(context);
-      var $source = $context.find('[data-drupal-date-formatter="source"]').once('dateFormat');
-      var $target = $context.find('[data-drupal-date-formatter="preview"]').once('dateFormat');
-      var $preview = $target.find('em');
+      var $context = $(context),
+          $source = $context.find('[data-drupal-date-formatter="source"]').once('dateFormat'),
+          $target = $context.find('[data-drupal-date-formatter="preview"]').once('dateFormat'),
+          $preview = $target.find('em');
 
       // All elements have to exist.
       if (!$source.length || !$target.length) {
@@ -25,8 +25,8 @@
        * @param {object} e
        */
       function dateFormatHandler(e) {
-        var baseValue = $(e.target).val() || '';
-        var dateString = baseValue.replace(/\\?(.?)/gi, function (key, value) {
+        var baseValue = $(e.target).val() || '',
+            dateString = baseValue.replace(/\\?(.?)/gi, function (key, value) {
           return dateFormats[key] ? dateFormats[key] : value;
         });
 
diff --git a/core/modules/system/src/Form/DateFormatFormBase.php b/core/modules/system/src/Form/DateFormatFormBase.php
index 69f1d95..9061d89 100644
--- a/core/modules/system/src/Form/DateFormatFormBase.php
+++ b/core/modules/system/src/Form/DateFormatFormBase.php
@@ -108,10 +108,10 @@ public function form(array $form, FormStateInterface $form_state) {
       '#maxlength' => 100,
       '#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')),
       '#required' => TRUE,
-      '#attributes' => array(
+      '#attributes' => [
         'data-drupal-date-formatter' => 'source',
-      ),
-      '#field_suffix' => ' <small class="js-hide" data-drupal-date-formatter="preview">' . $this->t('Displayed as %date_format', array('%date_format' => '')) . '</small>',
+      ],
+      '#field_suffix' => ' <small class="js-hide" data-drupal-date-formatter="preview">' . $this->t('Displayed as %date_format', ['%date_format' => '']) . '</small>',
     );
 
     $form['langcode'] = array(