diff --git a/core/modules/config_translation/src/FormElement/DateFormat.php b/core/modules/config_translation/src/FormElement/DateFormat.php
index 6395a92..8d404e3 100644
--- a/core/modules/config_translation/src/FormElement/DateFormat.php
+++ b/core/modules/config_translation/src/FormElement/DateFormat.php
@@ -20,7 +20,7 @@ class DateFormat extends FormElementBase {
   public function getTranslationElement(LanguageInterface $translation_language, $source_config, $translation_config) {
     /** @var \Drupal\Core\Datetime\DateFormatterInterface $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'));
+    $description = $this->t('A user-defined date format. See the <a href=":url" target="_blank">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' => $date_formatter->format(REQUEST_TIME, 'custom', $translation_config)));
 
     return [
diff --git a/core/modules/system/src/Form/DateFormatFormBase.php b/core/modules/system/src/Form/DateFormatFormBase.php
index 252fba4..0258ca0 100644
--- a/core/modules/system/src/Form/DateFormatFormBase.php
+++ b/core/modules/system/src/Form/DateFormatFormBase.php
@@ -104,7 +104,7 @@ public function form(array $form, FormStateInterface $form_state) {
       '#type' => 'textfield',
       '#title' => t('Format string'),
       '#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')),
+      '#description' => $this->t('A user-defined date format. See the <a href=":url" target="_blank">PHP manual</a> for available options.', array(':url' => 'http://php.net/manual/function.date.php')),
       '#required' => TRUE,
       '#attributes' => [
         'data-drupal-date-formatter' => 'source',