How Expiration Dates Are Written

Everyone · Explainer · Updated October 1, 2026 · LearnLife Editorial

What Are Expiration Dates in Plain Words?

Expiration dates are printed on products to tell you the last day the maker guarantees the item is safe to eat or use or that it will be at its best quality. These dates are especially common on food, medicines, and cosmetics. They help protect you by preventing the use of spoiled or harmful products. For example, eating expired dairy can cause stomach upset, and expired medicine may not work properly. These dates are a guide, not an exact cutoff, so you should also check a product’s smell, look, and feel before use.

The main point of expiration dates is safety and quality assurance. They assume proper storage, such as refrigeration for milk or keeping medicine away from heat. Beyond the expiration date, the manufacturer no longer guarantees safety or effectiveness. This doesn’t always mean the product instantly becomes dangerous, but its quality or safety may decline. For instance, crackers past their date might taste stale but not cause harm, while raw chicken past its date could be unsafe.

How Are Expiration Dates Written? A Clear Example with Details

Expiration dates can be presented in different ways on packaging, depending on the product and company. Most U.S. products show the date as month/day or month/day/year. Some imported items may use day/month/year. Dates can be fully numeric or include an abbreviated month name. Common labels you’ll see are “EXP,” “Use By,” “Best Before,” “Sell By,” and others.

Example:

Suppose you buy a jar of peanut butter labeled “Use By 06/15.” This means June 15 is the last recommended day to consume it for best quality and safety. If today is June 10, the peanut butter is still safe to eat. Another product might say “Best Before 08/23,” meaning it will taste best before August 23 but might still be safe afterward.

Sometimes only the month and year appear, like “Best Before 10/23.” This means the product is best used by October of that year. Other times, you might see a Julian date—a three-digit number representing the day of the year. For example, “EXP 120” means the 120th day of the calendar year. To find this date, count 120 days from January 1. If uncertain, check the package or manufacturer’s website for decoding.

Why Does Understanding Expiration Date Formats Matter?

Knowing how expiration dates are written helps you avoid health risks and save money. Misreading a date might lead to eating spoiled food, causing illness, or throwing away food that’s still good, wasting money. For instance, if a label says “03/04” and you mistake it for March 4 instead of April 3, you might discard food too early or eat it too late.

Understanding these dates also helps with meal planning and grocery management. If you buy two containers of yogurt with different expiration dates, you can use the one expiring sooner first to reduce waste. It also helps you avoid confusion when buying imported or online products that may use different date formats.

What Are the Different Terms Used Alongside Expiration Dates and How Do They Differ?

Several terms on labels can be confusing because they sound similar but have different meanings:

• Expiration Date (EXP): The last date the product is guaranteed safe to use.
• Use By: The last date recommended to use the product for safety and quality.
• Best Before/Best By: The date up to which the product maintains its best flavor or texture. It may still be safe afterward.
• Sell By: A guideline for stores to manage inventory, not a safety date.
• Packed On/Manufactured On: The date the product was packaged or produced, not an expiration.
• Freeze By: The date by which you should freeze the product to keep quality.

Example:

Egg cartons often have a “Sell By” date, telling stores when to remove them from shelves, but eggs may still be safe for weeks if refrigerated. A bottle of salad dressing with a “Best Before” date may lose flavor after that date but isn’t necessarily unsafe.

Knowing these terms helps you decide when to use or discard items. For highly perishable foods like meat and dairy, follow “Use By” or “Expiration” dates strictly. For shelf-stable items, “Best Before” dates allow more flexibility.

How Can You Avoid Confusion When Reading Expiration Dates? Practical Tips

Here’s how to reduce confusion when checking expiration dates:

1. Read the Entire Label: Look for words like “EXP,” “Use By,” or “Best Before” to understand the date’s purpose.
2. Identify the Date Format: Determine if the product uses month/day/year or day/month/year by checking other products or the packaging.
3. Use Manufacturer Resources: Visit company websites or contact customer service for help decoding unfamiliar date codes.
4. Track Dates at Home: Keep a list or use a phone app to record expiration dates once you buy products.
5. Label Opened Packages: Write the date you opened items like baby formula or supplements since freshness can decline faster after opening.
6. Follow Storage Instructions: Proper storage helps products last up to their expiration date. For example, refrigerate dairy and keep medicines in a cool, dry place.

Example Wording for Home Labeling:

Write on a container: “Opened 07/10, Use By 07/20” to remind yourself when to finish it.

What Should You Do If You’re Unsure About a Product’s Safety After the Expiration Date?

If you find a product past its expiration date, use these steps to decide whether to use it:

• Check Appearance: Look for mold, discoloration, or texture changes.
• Smell the Product: Off or sour smells often indicate spoilage.
• Taste a Small Amount (If Safe): Tasting is okay for some items but avoid this for raw meat or dairy if unsure.
• Inspect Packaging: Bulging cans or broken seals mean the product is unsafe.
• Ask a Professional: For medicines or supplements, consult a pharmacist.
• When in Doubt, Throw It Out: Don’t risk illness if you’re unsure.

Example:

If yogurt is past its “Use By” date but smells fresh and has no mold, it might be safe for a short time. However, if milk smells sour or is curdled, discard it immediately.

How Does Understanding Expiration Dates Help in Everyday Life?

Knowing how expiration dates work helps you keep your family safe and reduce food waste. It teaches you to shop wisely by choosing products with longer shelf lives or planning meals around products that expire sooner. It also helps you avoid using ineffective medicines or supplements.

For example, knowing that “Best Before” dates focus on quality lets you avoid tossing food that is still safe to eat. Understanding different date terms helps you teach children or others in your household about safe food handling. Finally, clarity on expiration dates improves your confidence when buying groceries, especially online or imported goods.

Frequently asked questions

Is it safe to eat food after the “Best Before” date?

Often, yes. “Best Before” dates indicate peak quality, not safety. Many foods remain safe to eat after this date if stored properly. Always check for signs of spoilage like mold or odor before eating.

How can I tell if a medicine is expired?

Check the expiration date on the packaging. If missing or unclear, don’t use the medicine. Expired medicines may be less effective or unsafe. Consult a pharmacist for advice.

Can freezing extend a product’s expiration date?

Freezing slows spoilage and can extend the usability of many products but does not reset expiration dates. Label frozen foods with the freeze date and follow safety guidelines for thawing and use.

What does “Sell By” mean on food packaging?

“Sell By” is a date for stores to manage inventory, not a safety indicator. Many foods are safe to consume after this date if stored properly but should be used soon after.

What should I do if an expiration date is smudged or missing?

Look for other clues like production or lot numbers. If uncertain, rely on storage guidelines and sensory checks. For medicines or important products, contact the manufacturer or a healthcare professional.