According to the Ministry of Business, Innovation and Employment, the best-before date indicates the ideal time by which food should be eaten.
It marks out when a product's quality will usually begin to diminish.
A use-by label, however, indicates how long food is safe for consumption, if it has been properly stored.
This is an absolute expiry date and should not be tested.
WHY IS THERE A DIFFERENCE?
The NZ Nutrition Foundation says foods are assigned a label depending on how fast they deteriorate.
Basically, it depends on what happens when the food or drink is kept, says chief executive officer Sue Pollard.
"Some foods go off, get contaminated and can cause food poisoning quite easily," she says.
These foods receive use-by labels.
Foods which might be less tasty but still safe to eat usually get best-before labels.
WHAT IF I BUY SOMETHING THAT HAS EXPIRED?
The 1981 Food Act requires that all food sold must be fit for human consumption. Therefore, selling food past its use-by date is illegal.
However, products can still be sold after the best-before date has expired. These are often offered at a discount.
Supermarkets will sell packaged meat at a cheaper rate when it is close to its best-before date, Pollard says.
"Fresh meat will keep for quite a long time after that."
WHAT IF THERE IS SOMETHING WRONG WITH IT?
The Consumer Guarantees Act says all goods sold must be of acceptable quality.
Keeping grocery receipts will help in getting a refund if you purchase sub-standard food.
It is also illegal to sell food after its use-by date has expired, warns Pollard.
Any concerns around food safety should be reported to the New Zealand Food Safety Authority.
DOES THIS APPLY TO FRUIT AND VEGETABLES?
Unpackaged foods such as loose fruit are not required to have a date label. Foods which can hold for more than two years are also exempt.
Purchasing a bag of floury apples will not equate to a refund either, Pollard warns.
"It's just a matter of recognising what the fruit is like when you buy it - that's a skill you probably acquire over time."
Shoppers after the best fruit and vegetables should follow the "fresh is best" mantra, says the Federation of Family Budgeting Services.
Chief executive officer Raewyn Fox recommends local farmers' markets for fresh produce.
HOW LONG IS TOO LONG?
Generally, things keep better if they're in the fridge, are well-sealed and out of sunlight, Pollard says. Following storage instructions on packaging labels will also help food last longer and prevent costly wastage.
And once food is opened and exposed to air, the use-by or best-before dates do not apply.
"Once you open a product, you do with it what you would do with a similar fresh product.
"Many canned foods will last for years and years, but once you open them they may have a shelf life of only a week or so."
Several things contribute to the shelf-life of a product. They include the type of product, how it is stored and whether it is preservative and additive free.
The NZ Nutrition Foundation says: "If in doubt, throw it out."
WHAT ABOUT STORING FOOD?
Poor storage practices can cause bugs such as salmonella and listeria to grow in food, warns the Ministry of Business, Innovation and Employment.
Any raw and cooked food needs to be separated, particularly meat.
The best place to store uncooked meat is at the bottom of the fridge because this is the coldest part, Pollard says.
People should also invest in a fridge thermometer as many are not the right temperature.
"It should be 4C or a little bit less."
Cleaning your fridge regularly and checking that the seals are working properly will also help.
