diff --git a/core/includes/common.inc b/core/includes/common.inc
index edd7c2d..52c95b1 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -1930,7 +1930,19 @@ function format_date($timestamp, $type = 'medium', $format = '', $timezone = NUL
 
   // Call date_format().
   $settings = array('langcode' => $langcode);
-  return $date_time->format($format, $settings);
+  $formatted_date = $date_time->format($format, $settings);
+
+  $context = array(
+    'date_time' => $date_time,
+    'timestamp' => $timestamp,
+    'type' => $type,
+    'format' => $format,
+    'timezone' => $timezone,
+    'langcode' => $langcode,
+  );
+  drupal_alter('format_date', $formatted_date, $context);
+
+  return $formatted_date;
 }
 
 /**
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 5e3582f..c1a1a3b 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -3950,6 +3950,29 @@ function hook_filetransfer_info_alter(&$filetransfer_info) {
 }
 
 /**
+ * Alter the formatted date.
+ *
+ * A module may implement this hook in order to alter the formatted date string.
+ *
+ * @param string $formatted_date
+ *   The formatted date.
+ * @param array $context
+ *   An associative array containing:
+ *   - date_time: The DrupalDateTime object with the date to format.
+ *   - timestamp: The UNIX timestamp to format.
+ *   - type: The format to use as passed to format_date().
+ *   - format: If type is 'custom', a PHP date format string suitable for input
+ *     to date().
+ *   - timezone: The time zone as passed to format_date().
+ *   - langcode: The language code as passed to format_date().
+ *
+ * @see format_date()
+ */
+function hook_format_date_alter(&$formatted_date, array $context) {
+  $formatted_date .= ' ' . $context['timezone'];
+}
+
+/**
  * @} End of "addtogroup hooks".
  */