diff --git a/usr.bin/grdc/grdc.6 b/usr.bin/grdc/grdc.6
index 5226a6b2a9c7..269b8984ec3e 100644
--- a/usr.bin/grdc/grdc.6
+++ b/usr.bin/grdc/grdc.6
@@ -1,33 +1,45 @@
 .\" $FreeBSD$
 .Dd September 25, 2001
 .Dt GRDC 6
 .Os
 .Sh NAME
 .Nm grdc
 .Nd grand digital clock (curses)
 .Sh SYNOPSIS
 .Nm
 .Op Fl st
 .Op Ar n
 .Sh DESCRIPTION
 .Nm
 runs a digital clock made of reverse-video blanks on a curses
 compatible VDU screen.
 With an optional numeric argument
 .Ar n
 it stops after
 .Ar n
 seconds (default never).
 The optional
 .Fl s
 flag makes digits scroll as they change.
 The optional
 .Fl t
 flag tells grdc to output the time in a 12-hour format.
 In this curses mode implementation,
 the scrolling option has trouble keeping up.
+.Sh ENVIRONMENT
+.Bl -tag -width Ds
+.It Ev TZ
+The time zone to use for displaying the time.
+It is normally specified as a pathname relative to
+.Pa /usr/share/zoneinfo ,
+though see
+.Xr tzset 3
+for more information.
+If this variable is not set, the time zone is determined based on
+.Pa /etc/localtime .
+.El
 .Sh AUTHORS
 .An -nosplit
 .An Amos Shapir ,
 modified for curses by
 .An John Lupien .