Question: My teenage daughter refuses to drink milk after the date on the carton, but I’ve always felt it was safe for at least a few days. Is this true?
Answer: Yes, milk that has been properly stored will generally remain drinkable for about one week after the "sell-by" date on the package.
That’s the general case, mind you — as the Dairy Council of California points out, several factors will influence what happens in your particular fridge once the milk’s sell-by date has passed.
Keeping your milk continuously refrigerated and sealing the container well after each use will go a long way toward keeping your milk fresh. So too will making sure that the temperature of your refrigerator remains at or below 40° Fahrenheit at all times.
If milk develops an off odor, flavor or appearance, you should always discard it.
(Note: This refers to “sell-by” terminology used in the United States; practices in other countries may differ.)