There are two types of dating that are usually displayed on a food product: "Open dating" and "Closed or coded dating." Even if the "use by" or "sell by" date hasn't passed, foodborne pathogens can still contaminate foods that aren't properly stored and handled.
Always wash your hands, separate raw foods from ready-to-eat foods, cook to proper temperatures and refrigerate foods promptly.
The two types of date marking are use by dates and best before dates.
The food supplier is responsible for placing a use by or best before date on food.
Foods that have a best before date can legally be sold after that date provided the food is fit for human consumption.