diff -u b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
--- b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Entity/Feed.php
@@ -157,17 +157,27 @@
 
     $fields['url'] = FieldDefinition::create('uri')
       ->setLabel(t('URL'))
-      ->setDescription(t('The URL to the feed.'))
+      ->setDescription(t(('The fully-qualified URL of the feed.'))
       ->setRequired(TRUE)
       ->setSetting('max_length', NULL)
       ->setDisplayOptions('form', array(
         'type' => 'uri',
-        'weight' => -4,
+        'weight' => -3,
       ));
 
-    $fields['refresh'] = FieldDefinition::create('integer')
-      ->setLabel(t('Refresh'))
-      ->setDescription(t('How often to check for new feed items, in seconds.'));
+    $intervals = array(900, 1800, 3600, 7200, 10800, 21600, 32400, 43200, 64800, 86400, 172800, 259200, 604800, 1209600, 2419200);
+    $period = array_map('format_interval', array_combine($intervals, $intervals));
+    $period[AGGREGATOR_CLEAR_NEVER] = t('Never');
+
+    $fields['refresh'] = FieldDefinition::create('list_integer')
+      ->setLabel(t('Update interval'))
+      ->setDescription(t('The length of time between feed updates. Requires a correctly configured <a href="@cron">cron maintenance task</a>.', array('@cron' => url('admin/reports/status'))))
+      ->setRequired(TRUE)
+      ->setSetting('allowed_values', $period)
+      ->setDisplayOptions('form', array(
+        'type' => 'options_select',
+        'weight' => -2,
+      ));
 
     $fields['checked'] = FieldDefinition::create('timestamp')
       ->setLabel(t('Checked'))
diff -u b/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php b/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php
--- b/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/FeedFormController.php
@@ -27,18 +27,14 @@
     $period = array_map('format_interval', array_combine($intervals, $intervals));
     $period[AGGREGATOR_CLEAR_NEVER] = $this->t('Never');
 
+    // @todo: convert to a language selection widget defined in the base field.
+    // Blocked on https://drupal.org/node/2226493 which adds a generic language widget.
     $form['langcode'] = array(
       '#title' => $this->t('Language'),
       '#type' => 'language_select',
       '#default_value' => $feed->language()->id,
       '#languages' => Language::STATE_ALL,
-    );
-
-    $form['refresh'] = array('#type' => 'select',
-      '#title' => $this->t('Update interval'),
-      '#default_value' => $feed->getRefreshRate(),
-      '#options' => $period,
-      '#description' => $this->t('The length of time between feed updates. Requires a correctly configured <a href="@cron">cron maintenance task</a>.', array('@cron' => url('admin/reports/status'))),
+      '#weight' => -4,
     );
 
     return parent::form($form, $form_state, $feed);
only in patch2:
unchanged:
--- a/core/modules/aggregator/aggregator.info.yml
+++ b/core/modules/aggregator/aggregator.info.yml
@@ -7,3 +7,4 @@ core: 8.x
 configure: aggregator.admin_settings
 dependencies:
   - file
+  - options