Question: I’ve got some yogurt in the fridge and I just discovered that the sell-by date was a week ago. Is it still safe to eat?
Answer: Most likely it is. Yogurt that has been properly stored will generally remain safe for at least 1 to 2 weeks after the "sell-by" date on the package.
As the food safety specialists at Clemson University’s Cooperative Extension point out, this assumes that the temperature of your refrigerator remains at or below 40° Fahrenheit at all times. Bear in mind, too, that the longer you keep yogurt, the stronger its taste will become.
If mold appears on yogurt, or if it develops an off odor, flavor or appearance, you should always discard it immediately.
(Note: This refers to “sell-by” terminology used in the United States; practices in other countries may differ.)