Boston City Councilor John R. Connolly set off an uproar last month when he went into public school kitchens and snapped photos of frozen meat and cheese dated as far back as 2009. Food past the stamped expiration date packs an emotional punch, and not just when schoolchildren are involved.

“My husband constantly thinks I’m trying to poison him,’’ Amy Masters Ribner, of Newton, a “Chronicle’’ producer, says of Josh Ribner. “He’s like the food police. He’ll go through the fridge asking, ‘How old is this? How old is this?’ This is a man who thinks Coke is a food group, yet he’s afraid to be poisoned by mustard. How bad can a condiment be?’’

Who even knows? Nobody, really. A study by ShelfLifeAdvice.com and Harris Interactive concluded that more than three-quarters of US consumers mistakenly believe certain foods are unsafe to eat after the expiration date has passed. “The dates on food packages are very conservative,’’ Joe Regenstein, a professor of food science at Cornell University, and a member of the website’s scientific advisory board, said when the survey was released last year. “If the product was stored properly, it should last well beyond the date on the package.’’

Even if the FDA and the USDA also say food can be safe beyond the expiration date if storage conditions are optimal, there is enough wiggle room to give ammunition to both sides — the uptight and the lax. With frightening stories about food-borne illnesses common, and the lousy economy making wasting food even more painful, it’s no wonder those tiny printed dates have the power to pit people against friends, family, even themselves.

In Jamaica Plain, Carly Burton, director of public policy and political affairs for a Boston nonprofit organization, says her wife, an associ ate scientist at a biotech company, takes a “unique’’ approach to expiration dates: She follows them. What’s a reasonable date-ignorer like Burton to do? While she’s never secretly changed a date or blacked one out with a marker, she has, she admits, cooked food that is recently expired and served it to her beloved, Melissa Berman.

Sometimes she worries she might sicken her spouse, but Burton’s behavior is not her fault. It’s what she was taught. “I grew up in a household where the expiration date had a meaning, but . . . ’’

At that point, Berman steps forward to set the record straight about her mother-in-law: “She has a blatant disregard for expiration dates.’’

When it is suggested that ignoring expiration dates may be hereditary, Berman is quick with her response: “What’s hereditary is the ability to survive expired food.’’