diff --git a/change_log.txt b/change_log.txt
index b2395dca..e1fb1f25 100644
--- a/change_log.txt
+++ b/change_log.txt
@@ -1,4 +1,7 @@
  ===== 3.1.28-dev===== (xx.xx.2015)
+ 01.08.2015
+  - update DateTime object can be instance of DateTimeImmutable since PHP5.5 https://github.com/smarty-php/smarty/pull/75
+  
  31.07.2015
   - optimize {foreach} and {section} compiler
 
diff --git a/libs/plugins/shared.make_timestamp.php b/libs/plugins/shared.make_timestamp.php
index 7c94e5f5..f87d40c7 100644
--- a/libs/plugins/shared.make_timestamp.php
+++ b/libs/plugins/shared.make_timestamp.php
@@ -21,8 +21,8 @@ function smarty_make_timestamp($string)
     if (empty($string)) {
         // use "now":
         return time();
-    } elseif ($string instanceof DateTime) {
-        return $string->getTimestamp();
+    } elseif ($string instanceof DateTime || (interface_exists('DateTimeInterface', false) && $string instanceof DateTimeInterface)) {
+        return (int) $string->format('U'); // PHP 5.2 BC
     } elseif (strlen($string) == 14 && ctype_digit($string)) {
         // it is mysql timestamp format of YYYYMMDDHHMMSS?
         return mktime(substr($string, 8, 2), substr($string, 10, 2), substr($string, 12, 2),