From LedHed's Wiki
Overview
Each user can have their own crontab. This allows users to schedule jobs to run at specific intervals.
View Job List
crontab -l
Add/Edit Job
crontab -e
Reference
http://en.wikipedia.org/wiki/Cron
http://www.freebsd.org/cgi/man.cgi?query=crontab&sektion=1&apropos=0&manpath=FreeBSD+9.0-RELEASE