They remain edible for months and even years, but they will eventually start tasting like the freezer.
When kept in a cool dark place, canned foods remain edible for years.
Pasta, rice, lentils will keep for years. Snack bars, crackers and cookies may perhaps lose some of their freshness and their “crunch”, but are certainly still edible after a few months. Chocolate keeps for 1 year after the date and honey forever.
The vinegar contained in most condiments preserves them for a long time: Ketchup, mustard, sauces and vinaigrette are usually good for months after their expiry date. Mayonnaise a little less so, because of the eggs it contains.
As for condiments, their colour may change due to light (brown ketchup), but it does not change the taste.
As for the fresh milk, if kept between 2° and 4°C some “premium” brands can reach 2 weeks after the date. The trick is to take what you need and put it right back in the fridge.
I once kept an open container of 35% cream 5 weeks after the expiry date (I was out of town) and it was still good.