utmp(5) was present in v1

https://www.bell-labs.com/usr/dmr/www/man51.pdf
Earliest version of wtmp I could find was in v3
https://minnie.tuhs.org/cgi-bin/utree.pl?file=V3/man/man5/wtmp.5

share/man/man5/utmp.5

@@ -1,4 +1,4 @@
-.\"	$NetBSD: utmp.5,v 1.16 2010/03/22 18:58:32 joerg Exp $
+.\"	$NetBSD: utmp.5,v 1.17 2019/09/01 19:04:59 sevan Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)utmp.5	8.2 (Berkeley) 3/17/94
 .\"
-.Dd May 14, 2003
+.Dd September 1, 2019
 .Dt UTMP 5
 .Os
 .Sh NAME
@@ -210,10 +210,12 @@ file.
 .Sh HISTORY
 A
 .Nm utmp
-and
+file format appeared in
+.At v1 .
+The
 .Nm wtmp
 file format appeared in
-.At v6 .
+.At v3 .
 The
 .Nm lastlog
 file format appeared in