I always enjoy buying old things on sale at the super market. My favourite is cheese (not that there is much of a selection in rural Japan :-P). They've got this relatively nice artisan gouda in the grocery store which is insanely expensive. Once it goes past the best before date, it's marked half price. I'm always thinking, "Thanks for ageing my cheese" as I buy it ;-)

My wife calls me the "Half price king" because I wander around looking for things. Bizarre stuff you can get on sale includes wine (where they have no room on the shelves and have to sell their old stock to accommodate the new stock -- companies pay for placement!), but also stuff like cultured butter or yogurt (yogurt fermented with a theromophilic culture by a reputable supplier will last months and months), natto (well... I like it), pickles, etc. I also look for beef that's gone off colour, or deep sea fish that's been kept frozen. Also, fruits are often great just before they go off, so as long as you intend to eat it that day, you can often get really good discounts.

On the downside, I have to warn my wife about buy bread and spices on sale -- some things really go down hill with age.

In the UK, and I guess there are similarities elsewhere, food dates come in two forms.

"Best before" is product quality information. "Use by" is product safety information. If a product says "best before mm/yyyy" you can use the product after that. There'll be a gradual deterioration in quality. But it may well be safe for years after the date (depending how it's stored and whether the packaging stays in shape).

"Use by" means you risk illness if you eat it after the date. Obviously there's a bit of a safety margin built in, and some people are at much higher risk of illness than others.

For what it's worth, I'm in Texas and the dates printed on the prepackaged food in my fridge have similar language; some say "best before", some say "best by", and some say only "b.b." (which is disturbingly ambiguous). I'm sure I've seen products with "use by" or "expires on" labels here though, but I've never interpreted any of them differently. Just seems like a guideline to me, I guess. Products that have an admonishment to "once opened, use within 7 days", like packaged deli meat, get my more thorough smell test.

But I have two questions for you:

- where I live, most beer has only a "born on" date, and apparently never expires. What about over there?

- and my only test for egg goodness is that good ones sink and bad ones will float. I've heard that eggs in the UK are prepared for sale differently - does this test work for them?

Cheese though. Obviously it probably won’t make you sick, but when you see mold on the surface it has permeated the cheese. Recommend throwing it out. All the other stuff you mentioned is fine.

The USDA claims that in the case of hard cheese, it is sufficient to trim 1 inch from the mold:

https://www.fsis.usda.gov/wps/wcm/connect/a87cdc2c-6ddd-49f0...

As far as I understand there are no pathogenic moulds that will grow on hard cheese (it is too acidic). Just to be clear, this is not the case for soft cheeses (camembert, brie, some blue cheeses, really soft washed rind cheeses, etc), though. If that starts to go off, throw it out. The pH can get up all the way to 7 on those cheeses, so they aren't safe.

I’ve lived my whole life breaking this advice. No ill effects yet!

Me too, more often in my student days rather than recent past though.

If I found mould on my cheese I'd just slice it off, and eat the rest. (Though now I think about it, if I saw bread with mould on it I'd throw the whole loaf away.)

I agree, the bread-type mold must be different from the cheese-type. Maybe the loose structure of the bread makes it easy for the mold to spread thin and quick through the air gaps, while in cheese it propagates more slowly.

Idk, but if there's mold on one part of the loaf the whole thing smells funky.

Hard cheeses are acidic (usually around a pH of 5) and salty. There are only a few types of mould that will grow on it. Lots of cheese producers grow wild mould on the rind of the cheese and it is perfectly edible.

What?

Cheese is already off milk, many have added mold, its a feature.

They have specific varieties of added mold, such as particular Penicillium species, that don't produce chemicals that make you sick. Plenty of other molds have the potential to be bad if you ingest their output.