The answer most shoppers do not expect: except for infant formula, federal law requires no dates on packaged food at all. Sell-by dates tell stores how long to display a product; best-if-used-by dates are the manufacturer's quality estimate; neither marks when food becomes unsafe, per FDA and USDA Food Safety and Inspection Service guidance. Only infant-formula use-by dates carry a federal requirement, and the USDA estimates 30 to 40 percent of the US food supply goes uneaten, with label confusion a documented contributor.
This site publishes information, not medical or legal advice. The definitions here come from named agencies, and food-safety judgments for vulnerable households — infants, elderly family members, immunocompromised people — belong with a clinician or the USDA's safety resources rather than a date stamped on a carton.
What does each date phrase actually mean?
The USDA's Food Safety and Inspection Service, which regulates meat, poultry, and egg products, sorts the vocabulary into three. A sell-by date tells the store how long to offer the product for sale — a stocking instruction for retailers, not a warning for shoppers. A best-if-used-by or best-by date is the manufacturer's estimate of when the product will be at peak flavor and texture; food past it may taste duller but is not automatically hazardous, per the agency's guidance. A use-by date is the last date recommended for peak quality, again not a safety cutoff in the regulatory sense. In every case, the date speaks to quality as the packer defines it, except in formula, where the FDA-required use-by date guarantees nutrient content declared on the label.
Which products are actually required to carry dates?
Two categories, essentially. Infant formula must carry a use-by date under federal regulation, 21 CFR Part 107, because its nutrient levels must hold through that date; selling formula past its date is prohibited. Everything else is governed by state law, which varies widely — more than 20 states require dates on dairy or other perishables, several states have prohibited selling past-date products, and others require nothing, per surveys compiled by food-law researchers including the Harvard Food Law and Clinic. The voluntary labels manufacturers print elsewhere follow no uniform federal standard, which is why the phrases differ product to product and why the FDA asked industry in 2019 to standardize on best if used by for quality dates.
The label vocabulary, in one table
| Phrase | Who it addresses | What it marks | Federal requirement |
|---|---|---|---|
| Sell by | Retailers | How long to display stock | No |
| Best if used by / best by | Consumers | Peak quality estimate | No |
| Use by | Consumers | Last date for peak quality | No, except infant formula |
| Expiration date | Varies | Undefined federally; state rules vary | No |
A sell-by date is a conversation between a manufacturer and a grocery manager. The shopper was never the audience — and safety was never the topic.
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How much does misreading the labels cost?
The USDA's Economic Research Service estimated in 2014 that 30 to 40 percent of the US food supply, measured at the retail and consumer levels, went uneaten — an estimate subsequent studies have treated as the federal benchmark. ReFED, a food-waste research nonprofit, and the Natural Resources Defense Council's 2013 analysis attributed a meaningful share of household waste to date-label confusion, with consumers discarding food that is wholesome out of safety fears. The waste compounds: food is the largest category in US landfills per the Environmental Protection Agency, and the agency's 2016 food-recovery hierarchy ranks prevention — which starts with not discarding sound food — above all downstream remedies.
Does food after its date become unsafe?
Not on any schedule the labels encode. Pathogenic bacteria — Salmonella, Listeria, pathogenic E. coli — do not announce themselves through dates, and the agencies are explicit that most date labels address quality, not microbial safety, per the Food Safety and Inspection Service's fact sheets. Perishable food safety depends on storage: the USDA's FoodKeeper guidance gives refrigerated storage times — raw poultry one to two days, ground meat one to two, steaks three to five, eggs three to five weeks — that matter far more than the printed date. Spoilage bacteria, which make food smell or feel wrong, are different organisms from pathogens; the odor warning is real for spoilage but unreliable for pathogens, which is why temperature control, not label arithmetic, is the safety variable the agencies emphasize.
What did agencies do about the confusion?
The FDA and USDA moved in the same direction in the late 2010s. The USDA's Food Safety and Inspection Service issued guidance in 2016 allowing the phrase best if used by on regulated products to signal quality, and the FDA followed in 2019 urging manufacturers to adopt the same phrase, both aiming to retire expiry and sell-by phrasing on consumer-facing packages. Roughly 80 percent of surveyed products carried best-by-style phrasing in industry studies cited by the agencies. Legislative proposals to standardize labels nationally have been introduced in Congress without passage, per congressional records, leaving the patchwork of state rules in place as of the mid-2020s.
When does a date or a smell actually mean discard?
The agencies' working rules: discard infant formula past its use-by date, always; discard perishable food left in the danger zone — above 40 degrees Fahrenheit for more than two hours — regardless of any date; follow USDA FoodKeeper storage windows for raw meats and seafood; and treat mold on soft foods and any off odor in perishables as grounds for disposal. Anyone who is pregnant, elderly, or immunocompromised faces Listeria and Toxoplasma risks where the margin between wholesome and hazardous is invisible even to careful inspection — for those households, the conservative call belongs with their own clinician's guidance rather than with a date or a sniff test.