It does depend. I just cleaned out our spice cabinet which had a lot of very old spices in it. o_o;;
But stuff like milk or bread... well for milk, I just smell it and make sure it hasn't turned. Unless if it's like only a bit left and clearly old, then I chuck it.
We usually buy two bread loaves and freeze one so then the date on it becomes a bit useless. So I just check it for any white or green spots and smell it to make sure it doesn't smell weird.
And, yeah, most things have a "Sell by" or "best by" date so you can't say exactly when the item has expired. Even expiration dates are usually conservative.