When you purchase food items at your local store or supermarket, you may notice a printed “Sell by” date, ”Use by” date or ”Best Before” date on the packaging or item itself and wonder just what that date really means. Getting informed about the true ”Shelf Life” of most popular food items, reveals that most food is still edible after these printed expiration dates have passed.

You may need to know that food can actually be sold after an expiration date. Stores are not legally required to remove food from the shelf once the expiration date has passed.  The expiration dates are strictly “advisory” in nature and are left entirely to the discretion of the manufacturer, thus not truly indicative of an items true Shelf Life.

So if you find yourself regretfully throwing away your food as soon as it hits that barely legible date on its packaging, you’re probably wasting way more food than you need to. Turns out, those dates aren’t necessarily hard expiration dates—and they definitely don’t all mean the same thing.

In a recent report for the Institute of Food Technologists, Director of the Institute for Food Safety and Health at the Illinois Institute of Technology, Dr. Bob Brackett breaks down the difference between those “use-by,” “sell-by,” and “best-by” labels.

Unless a use-by or best-by label is followed by the words ”for safety,” these dates refer to the quality of your products—so there’s no need to panic if you’re a few days past the “use-by” date.

“You can probably eat it and not worry about it, just understand it’s not the best quality anymore,” says Brackett. There is one caveat: If you’ve opened the product already. Once you do that, things become a little less precise because the food is at risk of being contaminated by your or the environment, something the date on the packaging doesn’t account for.

If you’re like most people, you rely on sensory cues like a sour smell, slimy texture, or weird color to tell if your food has gone bad. But Dr Brackett says that disease-causing organisms are invisible and aren’t behind spoilage problems. So just because your milk hasn’t gone sour yet doesn’t mean it hasn’t gone bad.

While Brackett says many are pushing for a more regulated system to avoid consumer confusion, there is no standardized rule that determines which types of products get use-by dates and which get sell-by stamps. Manufacturers do their own shelf-life studies and indicate the quality timeline of their products however they deem fit.