If a food smells/tastes funny, don't eat it. Simple as that. Some things last basically forever, like salt. Pasta can be kept for years after date. Cans technically never expire (unless there's small tears in the metal, so be careful with dented cans).

I'm in Europe, so I don't know how it is in the US, but here there's two different dates on stuff: "best before" and "use before". Use before items usually spoil easier (like milk, yogurt, cheese, meat, fruit, veg...) so you just have to look for yourself if they're still good. Best before just means the food is guaranteed by the company to be fresh before that date, but after that it's up to you. Often this means the product will lose flavor or the texture might change, but it'll still be good to eat for a very long time.