After the installation of the /usr/share/zoneinfo, run tzsetup if

/var/db/zoneinfo exists.

MFC after:	1 week

share/zoneinfo/Makefile

@@ -54,4 +54,24 @@ beforeinstall:
 	${INSTALL} -o ${BINOWN} -g ${BINGRP} -m ${NOBINMODE} \
 	    ${.CURDIR}/zone.tab ${DESTDIR}/usr/share/zoneinfo/
 
+afterinstall:
+	@#
+	@# If the file /var/db/zoneinfo exists, and it is owned by root:wheel,
+	@# and the contents of it exists in /usr/share/zoneinfo, then reinstall
+	@# it.
+	@#
+	@if [ -f ${DESTDIR}/var/db/zoneinfo -a -O ${DESTDIR}/var/db/zoneinfo \
+	    -a -G ${DESTDIR}/var/db/zoneinfo ]; then \
+		zf=$$(cat ${DESTDIR}/var/db/zoneinfo); \
+		if [ -f ${DESTDIR}/usr/share/zoneinfo/$${zf} ]; then \
+			if [ ! -z "${DESTDIR}" ]; then \
+				optC="-C ${DESTDIR}"; \
+			fi; \
+			echo "Updating /etc/localtime"; \
+			tzsetup ${optC} -r; \
+		fi; \
+	else \
+		echo "Run tzsetup(8) manually to update /etc/localtime."; \
+	fi
+
 .include <bsd.prog.mk>