Package: cron Version: 3.0pl1-136 Severity: minor File: /usr/share/man/man5/crontab.5.gz
In section EXAMPLE CRON FILE please add # Run once every 9th day, even across week, month, and year boundaries: 33 22 * * * expr $(date +\%s) / 60 / 60 / 24 \% 9 > /dev/null || echo Wax the floor.