Running a process every N days

[danmcleran at yahoo.com]

What's the best way to run either an entire python process or a python
thread every N days. I'm running Python 2.4.3 on Fedora Core 5 Linux.
My code consists of a test and measurement system that runs 24/7 in a
factory setting. It collects alot of data and I'd like to remove all
data older than 30 days. My ideal solution would be something that
runs in the background but only wakes up to run every few days to
check for old data.

Thanks,

Dan McLeran