For example, if CPU Load will be very high during daily backup at 22:00 ~ 00:00, we can schedule a daily downtime for the CPU Load check.
Add this entry in a file under /etc/cron.d/
# daily backup at 22:00, and takes less than 2 hours, so don't notify during this period: 00 22 * * * nagios /usr/lib/nagios/plugins/set_downtime.pl -H myhost -C svc -s "CPU Load" -b 0 -e 7200 -m fix -u nagios-admin -c "doing daily backup"