Having now learned this from experience, never ever eat dairy even one day after the expiration date. I ate yoghurt this morning one day after the date and I spent most of the morning being sick. Luckily for me, I recover from most things relatively quickly (meaning the gut-wrenching pain was over in 90 minutes), but that was one of the most intense 90 minutes of my life.
On the plus side, it tasted like strawberry going down and up. Gross.