Set PAM_TTY for remote displays too (used e.g. by pam_time)
--- xdm-1.1.11/greeter/greet.c.orig	2011-09-25 09:35:47.000000000 +0200
+++ xdm-1.1.11/greeter/greet.c	2011-09-26 16:43:55.211132926 +0200
@@ -535,6 +535,12 @@
 					(*pamhp, PAM_RHOST, hostname));
 		free(hostname);
 	    }
+
+	    /* "for graphical, X-based, applications the value for this
+	     * item should be the $DISPLAY variable." (pam_appl docs)
+	     */
+	    RUN_AND_CHECK_PAM_ERROR(pam_set_item,
+				    (*pamhp, PAM_TTY, d->name));
 	} else {			/* Displaying on local host */
 	    const char *ttyname = NULL;