I'm using the Referrers functionality within Prestashop 1.3.6 to credit sales to respective affiliates who send referrals through to my site.

The problem I encounter is that the cookie that registers the referrer url is set to expire in 6 months! This is too long, it means that if a visitor who has been referred to my site through affiliate XYZ, returns in 6 months to my site and then make a purchase, the affiliate XYZ will still be credited for this sale.

I need to set the expiration date to 14 days. Does someone know how to do this?
Thank you!

P.S. cookie expiration date can be checked through your browser (check security setting): clear all cookies, visit your site through a referrer site and cookies will start appearing in your browser including info regarding expiration date.