shutdown appeared as a standalone utility in 4.2BSD release, in 4BSD its a

target in init.
http://www.tuhs.org/cgi-bin/utree.pl?file=4BSD/usr/src/cmd/init.c
http://www.tuhs.org/cgi-bin/utree.pl?file=4.2BSD/usr/src/etc/shutdown.c

Amend HISTORY.
Bump date.

sbin/shutdown/shutdown.8

@@ -1,4 +1,4 @@
-.\"	$NetBSD: shutdown.8,v 1.31 2011/10/04 07:25:34 dholland Exp $
+.\"	$NetBSD: shutdown.8,v 1.32 2016/09/12 06:22:35 sevan Exp $
 .\"
 .\" Copyright (c) 1988, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)shutdown.8	8.2 (Berkeley) 4/27/95
 .\"
-.Dd October 4, 2011
+.Dd September 12, 2016
 .Dt SHUTDOWN 8
 .Os
 .Sh NAME
@@ -240,4 +240,4 @@ a colon (``:'') for backward compatibility.
 The
 .Nm
 command appeared in
-.Bx 4.0 .
+.Bx 4.2 .