Well, around here stores don't sell food past it's due date (I think it's against the law), but they sometimes discount things that are very close to the due date. I have no problem buying those for the discount, and using them or anything in my fridge that's past it's date, if it looks OK. When containers are unopened or full, they can keep quite a bit: yogourt can go 2-3 weeks after the date, milk 1-2 week if stuck in the back of the fridge, sealed cheddar cheese (ex. Kraft) I have eaten 2-3 months afterwards. The "cold chain" is much more important than any date. A half open milk pint in the fridge door will go bad way before the date specified. What do people think happens during the night, a food destroyer monster ?
Cereals, chips, processed dry food (pre-packaged cakes, ...), bread, up to a certain point they're mostly a bit dry or humid.
Mostly, I judge by the look & odor, like they did before food industrialization. Nature is made well, most food that is not good anymore & dangerous, you will notice.