Most dates printed on food, cosmetics, and household products are not true expiration dates. In the United States, infant formula is the only product with a federally mandated “use by” date. Every other date you see on packaging is a manufacturer’s estimate of when quality starts to decline, not a safety cutoff. Understanding how to find these dates, decode them, and judge whether a product is still good can save you money and reduce the roughly 30% of the U.S. food supply that gets wasted at the retail and consumer level, often because of date label confusion.
What Date Labels Actually Mean
There is no universal standard for date labeling in the United States. The USDA’s Food Safety and Inspection Service puts it plainly: there are no uniform or universally accepted descriptions used on food labels for open dating. That means the phrases you see vary by manufacturer, and almost none of them indicate safety. Here’s what the most common ones mean:
- Best if Used By / Best Before: The product will be at peak flavor or quality before this date. It’s not a safety date.
- Sell-By: This tells the store how long to keep the item on the shelf for inventory purposes. It’s directed at retailers, not you.
- Use-By: The last date the manufacturer recommends for peak quality. Still not a safety date, with one exception: infant formula.
- Freeze-By: The date by which you should freeze the product to lock in peak quality.
Federal regulations require that any calendar date on a food product include the month and day. For shelf-stable and frozen products, the year must also appear. The label must also include a phrase right next to the date explaining what it means, like “Best if Used By.” If you see a bare date with no explanation, the manufacturer isn’t following best practices.
How Manufacturers Set These Dates
The dates aren’t arbitrary guesses. Manufacturers use a combination of lab testing and sensory evaluation to estimate how long a product maintains acceptable quality. For food, this typically involves storing samples at different temperatures and checking them at regular intervals for signs of degradation. Scientists measure indicators like pH (which reveals fermentation), protein breakdown products (which signal spoilage), and microbial counts for bacteria like E. coli, Salmonella, and Listeria.
Sensory panels also play a role. Trained evaluators assess taste, smell, texture, and appearance over time to pinpoint when a product starts to noticeably decline. The final date on the label is usually set conservatively, well before the product would actually become unsafe, to account for less-than-ideal storage conditions in real life.
For products with long shelf lives, manufacturers often use accelerated stability testing. They store the product at higher-than-normal temperatures to speed up chemical reactions, then use mathematical models to extrapolate how the product would hold up over months or years at normal storage temperatures. This approach is common for shelf-stable foods, diagnostic reagents, and household chemicals.
Decoding Manufacturer Lot Codes
Some products don’t carry a plain-English date. Instead, they use a manufacturer code that encodes the production date, and you work backward from there using the product’s known shelf life. Bleach is a good example. Clorox uses a code like “G18099” where the first two characters identify the manufacturing plant, the third character is the last digit of the year (8 for 2018), and the remaining three digits represent the day of the year the product was made. Day 099 is April 9th. Since Clorox states their bleach has a one-year shelf life from the date of manufacture, you’d know that bottle is good through roughly April 2019.
If you encounter a code you can’t decipher, the manufacturer’s customer service line or website is your best resource. Many companies have lookup tools or will decode the stamp for you over the phone.
Why Storage Conditions Matter More Than the Date
A printed date assumes the product has been stored properly. Break that assumption, and the date becomes unreliable. Research on milk found that exposure at room temperature (25°C / 77°F) for just 3.2 hours reduces its shelf life by a full day. Scale that up to a grocery trip on a hot afternoon with a long drive home, and you can lose several days of usable life before the product even reaches your fridge.
Temperature is the biggest factor, but humidity and sunlight also accelerate degradation. Bleach, for instance, loses potency faster when stored in warm, bright locations. Cosmetics manufacturers test their products under varying temperature and humidity conditions specifically to estimate how real-world storage affects safety and performance. If you consistently store products in cool, dry, dark places, they will often last well beyond the printed date. If your pantry sits above your oven or your bathroom gets steamy, expect shorter usable life.
How to Judge Products Without a Clear Date
Cosmetics sold in the U.S. aren’t required to carry expiration dates. Some display a small open-jar symbol with a number like “12M,” meaning the product is intended to be used within 12 months of opening. If there’s no symbol at all, you’re relying on your own judgment.
For any product, your senses are a powerful and underrated tool. Food spoilage researchers at the University of Wisconsin describe spoilage as changes in texture, smell, taste, or appearance that make food undesirable, and these cues are often reliable even when a product is technically still within its printed date. Here’s what to watch for:
- Smell: Ammonia, sulfur, or sour odors indicate protein or sugar breakdown. Fish that smells strongly “fishy” is producing trimethylamine, a clear sign of bacterial activity. Rancid odors in fatty foods signal lipid degradation.
- Texture: Sliminess on meat, vegetables, or deli products is a hallmark of bacterial growth. Softening in produce means cell structures are breaking down. Bread that feels sticky or ropy has undergone starch degradation.
- Color: Green or gray discoloration on meat often comes from hydrogen sulfide produced by bacteria. Mold on bread or fruit shows as fuzzy patches in various colors. A chalky white film on baked goods can indicate yeast growth.
- Taste: Sourness in products that shouldn’t be sour points to fermentation by lactic acid bacteria. If something tastes “off” in any way, trust that instinct.
One important caveat: spoiled food is not always dangerous food, and dangerous food is not always spoiled. Some harmful bacteria produce no noticeable changes in appearance or smell. Sensory checks are a useful layer of protection, but they can’t detect everything.
The One Product With a True Expiration Date
Infant formula is the only food product in the United States where the “use by” date is required by FDA regulation and tied directly to safety and nutritional adequacy. Formula must contain the nutrients listed on the label through that date, and using it afterward means the nutrient levels may have dropped below what an infant needs. For every other food, the dates are about quality, and passing them does not automatically make the product unsafe.
A Practical Approach
For most groceries, treat “Best By” and “Sell By” dates as rough quality guides, not hard deadlines. Eggs, yogurt, hard cheeses, and many canned goods remain safe well past their printed dates when refrigerated or stored properly. Canned goods with no visible damage, bulging, or rust can last years. On the other hand, fresh deli meats, soft cheeses, and pre-cut produce are higher-risk items where you should pay closer attention to both the date and any sensory changes.
For household chemicals and cleaning products, check for a manufacturer code if no plain date is visible, and contact the company if you can’t decode it. Disinfectants that have passed their shelf life may no longer kill germs effectively even if they look and smell normal. For cosmetics, track when you opened the product and follow the period-after-opening guidance if one is printed. Eye products and liquid foundations are especially prone to bacterial contamination over time and deserve more caution than a powdered blush that sits dry in a compact.