Update: the promo is on the US website as well, here is the link.
The Alitalia Italian website is offering a 15% discount on tickets purchased by August 27 at Noon in Italy for travel between September 1 and November 30.
The discount actually applies to the full ticket cost, including taxes and fuel surcharges, and is valid on Alitalia flights throughout their route network. It’s valid on both coach and business class but not for premium economy.
You enter the e-Coupon discount code during the purchase process and then have to click ‘recalculate’ to see the new price.
The discount is not valid for the Classic Plus, children’s tickets, or on award tickets.
If you don’t want to mess with Google Translate on the Italian site while making a booking, it might be worth playing around with other country sites (and possibly varying the discount code). I haven’t gone through this but it’s possible that WKND15US might work on the US website or WKND15UK might work on the UK site.