You need to run a job at midnight when system usage is low, or you need to run jobs daily or weekly, but you would rather be sleeping, or enjoying life in some other way. Other good reasons for scheduling jobs include letting routine tasks happen automatically, or ensuring tasks are handled the same way every time. This tip helps you use the cron and at capabilities to schedule jobs periodically or at a single future time.
Linux and UNIX systems allow you to schedule jobs in the future, either just once, or on a recurring schedule. This article shows you how to schedule jobs periodically, and how to run a job at some future time.
Link: IBM