bsdinstall: Prompt user to set the date and time after selecting timezone

Not having the correct date and time makes many PKI based things not work

In 10 and 11, it can mean that Unbound, ntpd, and sshd won't start

Submitted by:	des (original patch)
MFC after:	7 days

usr.sbin/bsdinstall/scripts/time

@@ -26,4 +26,40 @@
 #
 # $FreeBSD$
 
+# Select timezone
 chroot $BSDINSTALL_CHROOT tzsetup
+
+# Switch to target timezone
+saved_TZ="$TZ"
+TZ="${BSDINSTALL_CHROOT}/etc/localtime"
+export TZ
+
+# Set date
+exec 3>&1
+DATE=$(dialog --backtitle 'FreeBSD Installer' \
+	--title 'Time & Date' \
+	--ok-label 'Set Date' \
+	--cancel-label 'Skip' \
+	--date-format '%Y%m%d%H%M.%S' \
+	--calendar '' 2 40 \
+2>&1 1>&3) && date $DATE
+exec 3>&-
+
+# Set time
+exec 3>&1
+TIME=$(dialog --backtitle 'FreeBSD Installer' \
+	--title 'Time & Date' \
+	--ok-label 'Set Time' \
+	--cancel-label 'Skip' \
+	--time-format '%H%M.%S' \
+	--timebox '' 2 40 \
+2>&1 1>&3) && date $TIME
+exec 3>&-
+
+# Switch back
+if [ -n "$saved_TZ" ]; then
+	TZ="$saved_TZ"
+else
+	unset TZ
+fi
+unset saved_TZ