diff --git a/docs/ref/templates/builtins.txt b/docs/ref/templates/builtins.txt
index 3ab8a5d73f..bdac556652 100644
--- a/docs/ref/templates/builtins.txt
+++ b/docs/ref/templates/builtins.txt
@@ -1251,7 +1251,10 @@ Available format strings:
     A                 ``'AM'`` or ``'PM'``.                     ``'AM'``
     b                 Month, textual, 3 letters, lowercase.     ``'jan'``
     B                 Not implemented.
-    c                 ISO 8601 Format.                          ``2008-01-02T10:30:00.000123``
+    c                 ISO 8601 format. (Note: unlike others     ``2008-01-02T10:30:00.000123+02:00``,
+                      formatters, such as "Z", "O" or "r",      or ``2008-01-02T10:30:00.000123`` if the datetime is naive
+                      the "c" formatter will not add timezone
+                      offset if value is a `naive datetime`_.)
     d                 Day of the month, 2 digits with           ``'01'`` to ``'31'``
                       leading zeros.
     D                 Day of the week, textual, 3 letters.      ``'Fri'``
@@ -1343,6 +1346,8 @@ used, without applying any localization.
 .. versionchanged:: 1.2
     Predefined formats can now be influenced by the current locale.
 
+.. _naive datetime: http://docs.python.org/library/datetime.html#datetime.tzinfo
+
 .. templatefilter:: default
 
 default