One of the most powerful and useful features that a Unix operating system has is the ability to schedule and run any task at any given time and day. This gives users the capability to schedule jobs to run. These jobs include but not limited to running cleanups, backups, updates, running specific applications amongst others.

The most common way to schedule these tasks are by using the commonly known Cron. Cron is basically a "clock daemon" that runs 24 hours and 7 days a week; it constantly checks to see if there are any jobs to run and if there is, it runs them.

For example, a crontab ('cron table') entry such as 50 1 15,30 * 5 payroll would run a hypothetical 'payroll' command at 1:50 AM on the fifteenth and thirtieth of every month, as well as every Friday.