Does it expire?

56 things and whether they actually go off. Several of the answers are the opposite of what the date on the packet suggests, because a great many printed dates are regulatory rather than biological.

Use by and best before are not the same thing

Use-by is a safety date and applies to things that become unsafe rather than merely unpleasant — it should be respected. Best-before is about quality, and most food is fine well past it. Conflating the two is responsible for an enormous amount of avoidable waste, and for occasional genuine risk in the other direction.

Does not expire

• Honey No. Honey does not spoil — edible honey has been recovered from Egyptian tombs. Crystallisation is not spoilage.
• Salt No. Salt is a mineral, and the date on the packet is a labelling convention rather than a biological fact.
• Sugar No. Sugar is itself a preservative — at that concentration nothing can grow in it.
• Bottled water The water does not expire. The date is about the plastic, and in some places about the law.
• Vinegar No. Vinegar is acidic enough to be self-preserving, and the murky blob in cider vinegar is harmless.
• Vanilla extract Pure vanilla extract does not expire — it is 35% alcohol. Imitation vanilla does slowly lose its flavour.

Indefinite if stored properly

• Frozen food Food held continuously at −18 °C is safe indefinitely. The dates are about quality only.
• Canned food An intact, undamaged can is safe more or less indefinitely. Quality is the limit, not safety.
• Hard cheese Cut the mould off hard cheese and eat the rest. This does not apply to soft cheese.
• White rice (uncooked) Effectively no, if it stays dry. Brown rice is the opposite — it goes rancid within months.
• Spirits (whisky, vodka, gin, rum) Unopened, indefinitely. Once opened, oxidation slowly flattens the flavour over a year or two — it never becomes unsafe.
• Dried pasta Plain dried pasta keeps for years. Egg pasta is the exception and has a real date.
• Motor oil Sealed oil keeps for years. Oil in an engine is limited by contamination and by time, not by mileage alone.
• Dried beans and pulses Safe indefinitely, but old beans get harder to cook and some never soften at all.
• Soy sauce Practically never in a sealed bottle — the salt content sees to that. Opened, it darkens and flattens over months.
• Maple syrup Unopened, indefinitely. Once opened it must be refrigerated, because mould will grow on the surface.
• Instant coffee It keeps for years unopened. Moisture is the only real enemy — it clumps and then it tastes of nothing.

Degrades in quality

• Eggs Eggs stay usable for weeks past the date on the box, and the float test tells you about age rather than safety.
• Medicines Most solid medicines keep much of their potency for years past the date — but a handful genuinely must not be used late.
• Petrol and diesel Petrol goes stale within months, and ethanol blends go faster because they absorb water.
• Batteries They self-discharge on the shelf, at very different rates by chemistry — and alkalines leak when flat.
• Wine The great majority of wine is meant to be drunk within a year or two. Very little of it improves.
• Chocolate It keeps far longer than the date. The white bloom on old chocolate is fat or sugar, not mould.
• Household bleach It loses strength within months and eventually becomes salt water. This surprises most people.
• Paint Unopened water-based paint keeps a few years; opened tins depend entirely on how well they were sealed.
• Flour White flour keeps 6-12 months; wholemeal goes rancid in 3-6 because the wheat germ oil oxidises.
• Dried spices and herbs They never become unsafe. They lose their aromatics — ground spices in 2-3 years, whole ones in 3-4.
• Olive oil Yes, and faster than most people expect. Extra virgin is at its best within about 18 months of harvest, not of purchase.
• Toothpaste It stays safe, but the fluoride stops doing its job — which is the only reason to use it.
• Hand sanitiser The alcohol evaporates. Below about 60 per cent it stops working, and you cannot tell by looking.
• Baking powder Yes, and it matters — it loses lifting power within about a year of opening. Test it before you bake.
• Bicarbonate of soda (baking soda) It lasts for years as a cleaner and a deodoriser, but its baking power fades once the tub has been opened a while.
• Coffee beans Never unsafe, but the clock that matters is the roast date, not the best-before — beans are past their best in about a month.
• Cooking oil (sunflower, rapeseed, vegetable) Yes — it goes rancid. Unopened it keeps a year or two; once opened, a few months in a warm kitchen.
• Butter It goes rancid rather than dangerous. A month or two in the fridge past the date, and up to a year frozen.
• Peanut butter Commercial peanut butter keeps 6-24 months; natural, unstabilised jars go rancid faster and prefer the fridge.
• Hydrogen peroxide It decomposes into water. An opened bottle is often plain water within six months.
• Superglue About a year opened, and the freezer genuinely extends it.
• Seeds Germination rate falls with age, and it falls at wildly different speeds depending on the species.
• Fire extinguishers Rechargeable ones need periodic servicing; disposable ones have a hard life of about twelve years.
• Pet food Dry food goes rancid faster than people expect, and the bag is part of the packaging for a reason.
• Tea It goes stale rather than off. Black tea holds up for years; green tea fades within a year.
• Ground coffee Safe for a long time, good for a short one. Grinding multiplies the surface area and staling takes days, not weeks.
• Oats Rolled oats keep 1-2 years. They do not spoil so much as go stale and eventually rancid.
• Nuts They go rancid rather than mouldy, usually within a year, and rancid is a taste problem rather than a poisoning one.

Has a real expiry date

• Milk Pasteurised milk keeps about a week past the date if it has stayed cold; UHT keeps for months unopened.
• Dried yeast Yes — it is alive, and the date is roughly when enough of it has died to matter. Proof it first.

Unsafe or ineffective after the date

• Sunscreen No. Sunscreen is regulated as a drug and must hold its stated SPF for three years — after that, assume it does not.
• Condoms No. Latex degrades, the date is regulated, and there is no visible warning before failure.
• Infant formula No — this is the one supermarket product whose date is legally binding and should be obeyed exactly.
• Mascara and eye makeup Three months after opening, and this is one of the cosmetic rules worth taking seriously.
• Child car seats Yes, genuinely — six to ten years from manufacture, moulded into the shell.
• Smoke alarms Ten years from manufacture, then the whole unit — not just the battery.
• Cycle and motorcycle helmets Five years is the usual manufacturer figure, and any single significant impact ends it immediately.
• Contact lens solution No. The date is real, and the opened bottle has a much shorter life than the printed date suggests.
• Plasters and sterile dressings The adhesive fails and, more importantly, the sterile seal is only guaranteed to the date.