25% Off at Old Navy - 10 Hours OnlyFrom 12 p.m. until 10 p.m. today, Sept. 8, you can save 25% off at Old Navy’s online store.25% Off at Old Navy - 10 Hours Only Just use the coupon code ONBDAY at checkout. This coupon excludes a few things – like Everyday Steals and leather outerwear – but you can still save quite a bit on your purchase.