/etc/cron.daily/diffmon just contains:
#!/bin/sh
if [ -r /etc/diffmon/diffmon.cf ] && [ -x /usr/bin/diffmon ] ; then
diffmon -c diffmon.cf
fi
But diffmon should not run if a systemd timer is available
(though this is not currently the case due to bug 999702,
to be fixed first).
For instance, /etc/cron.daily/man-db has:
if [ -d /run/systemd/system ]; then
# Skip in favour of systemd timer.
exit 0
fi
Similarly, /etc/cron.daily/plocate has:
# Skip if systemd timer is available.
if [ -d /run/systemd/system ]; then
exit 0
fi