I'm sure my fellow old fogeys here will remember what we used to do before expiry dates were printed on food: we'd open the packet & give it a sniff, and if it smelled OK we'd eat the product. That worked just fine!
I work with several retailers, so I agree with Anon on the difference between 'best before' and 'use by'. 'Best before' is just to inform you that your food will slowly start to go stale after that date but should still be safe to eat. 'Use by' is the serious one, because it means that the food will become unsafe to eat after that date. But manufacturers tend to be conservative with their dates, so you can usually eat a 'Use by' item the day after it has expired if it looks & smells OK, but you shouldn't risk stretching it out much longer than that.
I have a confession to make: I tend to buy a lot of my food on its expiry date, because our supermarkets tend to discount the price to get rid of it. I then either eat it that day or put it straight into the freezer to eat it at a later date. I've had some absolutely fantastic food this way that I would never buy otherwise due to it being ridiculously overpriced.
When eating fresh food, I will judge for myself whether to honour the expiry date. If it's something that could cause food poisoning (such as salmon or chicken) I won't touch it after that date. But if it's vegetables, fruit, yoghurt or eggs I'll use them up to several weeks past their date, provided they still look & smell ok.
