diff --git a/aggregator.install b/aggregator.install
index 9e2a101..11a88a2 100644
--- a/aggregator.install
+++ b/aggregator.install
@@ -334,3 +334,10 @@ function aggregator_update_last_removed() {
 function aggregator_update_1001() {
   config_set('aggregator.settings', 'aggregator_ssl_verification', TRUE);
 }
+
+/**
+ * Set default value for date_format setting.
+ */
+function aggregator_update_1002() {
+  config_set('aggregator.settings', 'date_format', 'D, m/d/Y - H:i');
+}
diff --git a/aggregator.pages.inc b/aggregator.pages.inc
index 0da4f08..cc325ec 100644
--- a/aggregator.pages.inc
+++ b/aggregator.pages.inc
@@ -333,7 +333,8 @@ function template_preprocess_aggregator_item(&$variables) {
     $variables['source_date'] = t('%ago ago', array('%ago' => format_interval(REQUEST_TIME - $item->timestamp)));
   }
   else {
-    $variables['source_date'] = format_date($item->timestamp, 'custom', variable_get('date_format_medium', 'D, m/d/Y - H:i'));
+    $format = config_get('aggregator.settings', 'date_format');
+    $variables['source_date'] = format_date($item->timestamp, 'custom', $format);
   }
 
   $variables['categories'] = array();
diff --git a/config/aggregator.settings.json b/config/aggregator.settings.json
index 6657f98..42fa980 100644
--- a/config/aggregator.settings.json
+++ b/config/aggregator.settings.json
@@ -13,5 +13,6 @@
     "feed_item_length": "fulltext",
     "teaser_length": 600,
     "clear": 9676800,
-    "aggregator_ssl_verification": true
+    "aggregator_ssl_verification": true,
+    "date_format": "D, m/d/Y - H:i"
 }