The tzoff argument is in minutes (behind/west of UTC), not seconds.

While here, also say that time = NULL and tzoff = NULL are independent.
The code doesn't yet implement that, but it will soon.

lib/libutil/parsedate.3

@@ -1,4 +1,4 @@
-.\"     $NetBSD: parsedate.3,v 1.13 2014/10/07 22:39:32 apb Exp $
+.\"     $NetBSD: parsedate.3,v 1.14 2014/10/08 17:06:18 apb Exp $
 .\"
 .\" Copyright (c) 2006 The NetBSD Foundation, Inc.
 .\" All rights reserved.
@@ -27,7 +27,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd October 7, 2014
+.Dd October 8, 2014
 .Dt PARSEDATE 3
 .Os
 .Sh NAME
@@ -46,15 +46,20 @@ function parses a datetime from
 .Ar datestr
 described in English relative to an optional
 .Ar time
-point and an optional timezone offset in seconds specified in
+point,
+and an optional timezone offset (in minutes behind/west of UTC)
+specified in
 .Ar tzoff .
-If either
+If
 .Ar time
-or
+is
+.Dv NULL 
+then the current time is used.
+If
 .Ar tzoff
-are
+is
 .Dv NULL ,
-then the current time and timezone offset are used.
+then the current time zone is used.
 .Pp
 The
 .Ar datestr