I could use cron, but I can't figure out if there's a way to set the right schedule. I can also check the date in Python, running the script via cron everyday, but checking the right date inside my (Python) script (which I assume has more powerful conditions).
I thought on limiting one run on fridays between 1 and 7, and the other one on fridays between  15 and 21. But this option would have a problem on months like 3/2013 which have 5 fridays.
Why not run the cron job each friday, but add code to write the last date ran in a file.  Check to see if two weeks has passed, rewrite the file, and run the rest of the cron job
How do I run a script on friday, once every two weeks?