diff --git a/UPDATING b/UPDATING
index e53bcca9dd06..d152766efad6 100644
--- a/UPDATING
+++ b/UPDATING
@@ -26,6 +26,13 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 13.x IS SLOW:
 	world, or to merely disable the most expensive debugging functionality
 	at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20101030:
+	The internal pre-processor in the calendar(1) program has been
+	extended to support more C pre-processor commands (e.g. #ifdef, #else,
+	and #undef) and to detect unbalanced conditional statements.
+	Error messages have been extended to include the filename and line
+	number if processing stops to help fixing malformed data files.
+
 20101026:
 	All the data files for the calendar(1) program, except calendar.freebsd,
 	have been moved to the deskutils/calendar-data port, much like the