What year did they require food companies to put expiration dates?

The requirement for food companies to put expiration dates on their products varies by country and by type of food.

- In the United States, the Food and Drug Administration (FDA) does not require expiration dates on most foods, with the exception of infant formula and some other specific products. However, many food companies voluntarily put expiration dates on their products as a way to indicate to consumers when the product is expected to be at its best quality.

- In the European Union, food companies are required to put expiration dates on all perishable foods that have a shelf life of less than two years. The expiration date format used in the EU is "day/month/year".

- In other countries, the requirements for expiration dates on food products may vary. It is always best to check the food labeling laws in the specific country where you are located to determine which foods are required to have expiration dates and what format is used.