This is usually accomplished using an operating system utility. If
you are using Windows, you can do this via the Windows Task Scheduler
(see http://www.iopus.com/guides/winscheduler.htm).

I am not a Linux user, but I believe that you use the "cron" utility
(see http://www.linuxhelp.net/guides/cron/) to do this on a system
running Linux.

Alan