how to run task periodically

[Mark Stapper]

 Hi,

I have a system that doesn't run 24/7/365.
I would like to make sure that some tasks (like updating the ports tree)
run weekly/monthly etc.
As the system isn't on 24/7 the cron job I usually run for these tasks
doesn't work as the machine isn't always running on the scheduled time.

So I need a utility that enable me to say: "if a week has passed since
the last run, run this command".
Is there such a utlility?
Cheers,
Mark

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 260 bytes
Desc: OpenPGP digital signature
Url : http://lists.freebsd.org/pipermail/freebsd-questions/attachments/20100818/23267774/signature.pgp