Crontab
Program

This tool will assist you setting up automated processes within
your web site. A cron job is a script which is set up to run
automatically at a given time of day.
A cron job may be set up to run at a particular time of the
day, day of the week, date of the month, or even to run a given
number of minutes into each hour.
Cron jobs can be useful for taking care of various scheduled tasks
for your account such as deleting out of date log files created by
a CGI script.

Utility for running scheduled tasks.
Minutes = 59-0
Hours = 0-24
Day = 1-7
As for a normal 24 hour digital clock, minutes run from 0 to 59
and hours run from 0 (midnight) to 23 (11 PM).
Example: If you set the day of the month to 31, the script will
be executed on the last day of the month.