To create the timer described here
systemd-run --on-calendar='*-*-01 12:00:00' --unit='unbound-root-hints' \
--remain-after-exit --description='Update root hints for unbound' --property='Type=exec' \
--property='After=network.target' --timer-property='Persistent=true' \
--timer-property='RandomizedDelaySec=2s' --timer-property='AccuracySec=1us' \
/usr/bin/curl -o /etc/unbound/root.hints https://www.internic.net/domain/named.cache