diff --git a/doc/config.rst b/doc/config.rst
index cf523cb2d..d0c9e5802 100644
--- a/doc/config.rst
+++ b/doc/config.rst
@@ -624,9 +624,10 @@ that use Sphinx's HTMLWriter class.
 
 .. confval:: html_last_updated_fmt
 
-   If this is not the empty string, a 'Last updated on:' timestamp is inserted
-   at every page bottom, using the given :func:`strftime` format.  Default is
-   ``'%b %d, %Y'`` (or a locale-dependent equivalent).
+   If this is not None, a 'Last updated on:' timestamp is inserted
+   at every page bottom, using the given :func:`strftime` format.
+   The empty string is equivalent to '%b %d, %Y' (or a
+   locale-dependent equivalent).
 
 .. confval:: html_use_smartypants
 
diff --git a/sphinx/quickstart.py b/sphinx/quickstart.py
index ed714d939..2409af72a 100644
--- a/sphinx/quickstart.py
+++ b/sphinx/quickstart.py
@@ -213,9 +213,10 @@ html_static_path = ['%(dot)sstatic']
 # directly to the root of the documentation.
 #html_extra_path = []
 
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-#html_last_updated_fmt = '%%b %%d, %%Y'
+# If not None, a 'Last updated on:' timestamp is inserted at every page
+# bottom, using the given strftime format.
+# The empty string is equivalent to '%%b %%d, %%Y'.
+#html_last_updated_fmt = None
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.