How to schedule for every two fridays with cron and/or at?

[Mike Fedyk]

Hi,

I have Amanda setup to run a daily backup Monday through Friday night.  
That works fine.

But now I want to add a full backup every two weeks on Friday night and 
I'm having trouble creating cron entries that don't have the commands 
running on the same day for full and daily backups.

The best I have come up with is to run "at 20:45 Friday + 14 days" and 
"at 20:45 Friday + 28 days" at the beginning of each month but I don't 
think that will handle the situation correctly if the weeks don't 
overlap correctly.

Any ideas on how to get this working would be very helpful.

Thanks,

Mike