One day the captain died at sea. After laying the captain's body to rest, the first mate led the entire crew into the captains quarters. The first mate turned pale and showed the paper to the others. Milk is spoiled when it starts to look like yogurt. Yogurt is spoiled when it starts to look like cottage cheese.
Cottage cheese is spoiled when it starts to look like regular cheese.
Regular cheese is nothing but spoiled milk anyway and can't get any more spoiled than it is already. If it makes you violently ill after you eat it, the mayonnaise is spoiled. Flour is spoiled when it wiggles. It never spoils. It is generally a good rule of thumb that cereal should be discarded when it is two years or longer beyond the expiration date.