SAN FRANCISCO (AP) — In Kimberley Kausen’s home, a passed “sell by” date on a jug of milk means different things to different family members. For her daughter, it means the jug belongs in the trash. For her husband, it means the milk is still good for a few more days.

Kausen, a chef and cooking teacher in Irvine, California, is more discerning and often uses her sense of smell before deciding what to do with the milk.

“I’ll put some thought into it, and if we’re talking about meat and poultry, I’m very cautious about that and for sure will do the smell test and the touch test,” she said.

The debate playing out in Kausen’s kitchen is repeated in homes across California and the country, where varying phrases on food packaging have long left shoppers unsure whether food is simply past its peak quality or unsafe to eat. The state is aiming to cut down on confusion — and the food waste it creates when people throw away food early — with a new food labeling law starting Wednesday.

It bans the use of “sell by” labels on food packaging, which experts say act as a guide for retailers on how long to display products on the shelves but are not an indicator of whether they are still safe to consume. Now, manufacturers selling food in California must use two standardized labels — a “Best if Used By” label for peak quality and “Use By” label for product safety.

Food manufacturers can choose to use either label or both, said Democratic Assemblymember Jacqui Irwin, the author of the bill.

California became the first state in the U.S. to standardize food labels when it approved the law in 2024 that seeks to reduce food waste and the state’s climate-warming emissions. New York state lawmakers recently approved a similar law that is awaiting Gov. Kathy Hochul’s signature.

Legislation addressing food labeling also has been proposed in Illinois, Maryland, Massachusetts, New Jersey and South Carolina, though it has not passed in those states.

Nick Lapis, director of advocacy at Californians Against Waste, which co-sponsored the bill, said food labels are the leading cause of household food waste. The “sell by” date labels have also been a problem for food banks in California because people consider those dates as meaning the food has expired, he said.

“We don’t need to build some kind of huge infrastructure and invest tons of money to solve this. We just need companies to use the same words across brands,” he said.

There are more than 50 different date labels on packaged food sold in stores, according to a 2022 report on food waste published by the University of Maryland. The information in the labels is largely unregulated and often does not relate to food safety.

“Consumers get confused and they just default to assuming that whatever date is on the package means ‘don’t eat it and throw it away’,” said Kumar Chandran, policy director at ReFED, a nonprofit focused on reducing food waste.

Chandran said California and New York’s approval of food-labeling laws has added momentum to the push for a national standard. A bipartisan bill that would establish uniform food labels is pending in Congress. The U.S. Department of Agriculture recommended a decade ago that food sellers should switch to “Best if Used By” labeling.

Currently, the only product that is regulated federally with date labels is infant formula.

With no federal regulations dictating what information labels should include, the stamps have led to consumer confusion — and nearly 20% of the nation’s food waste, according to the Food and Drug Administration. In California, that’s about 6 million tons of unexpired food that’s tossed in the trash each year.

Nate Rose, a spokesperson for the California Grocers Association, said some grocers have had to overhaul their labeling systems, but as a whole, the association has been supportive of the change.

The new labels will result in “a win-win where we can reduce food waste and consumers will find these decisions a little bit simpler,” he said, adding that shoppers will still find old labels in stores for months to come as grocers sell through the products that already have them.