diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index db3a652..121f73b 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -2034,6 +2034,12 @@
 variations are common.  To see the full set of format codes supported on your
 platform, consult the :manpage:`strftime(3)` documentation.
 
+For the same reason, handling of format strings containing Unicode code points
+that can't be represented in the charset of the current locale is also
+platform-dependent. On some platforms such code points are preserved intact in
+the output, while on others ``strftime`` may raise :exc:`UnicodeError` or return
+an empty string instead.
+
 The following is a list of all the format codes that the C standard (1989
 version) requires, and these work on all platforms with a standard C
 implementation.  Note that the 1999 version of the C standard added additional