diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index a822842..6ddf554 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -1955,6 +1955,11 @@ Notes:
    The :meth:`strptime` method can parse years in the full [1, 9999] range, but
    years < 1000 must be zero-filled to 4-digit width.
 
+   The :meth:`strftime` method will zero pad automatically for years < 1000 on
+   some platforms (e.g. Mac OS X, Windows), but not on others (e.g. Linux). Zero
+   padding can be forced on some platforms by using e.g. ``%4Y``, but this may
+   produce an invalid output or errors on other platforms.
+
    .. versionchanged:: 3.2
       In previous versions, :meth:`strftime` method was restricted to
       years >= 1900.