Generally, non-perishable items tend to contain an alphanumeric date that could include a letter to signify a month, a number with up to three digits that corresponds to a day and another number with up to two digits that represents a year. This is an example of closed or coded dating.
Closed or coded dating typically corresponds to the Julian calendar, in which the numbers one to 365 represent the days of the year in sequential order. Day one is January first, and day 365 is December 31. Coded dating is not necessarily an expiration date that references when the item becomes unsafe to eat. Non-perishable items are occasionally edible and safe past an expiration date, though the quality of flavor and texture often diminishes.
Open dating is another kind of food expiration dating. There are four types, which include sell-by, use-by, a pull date and a packing date. Use-by is the date that a manufacturer suggests consumers use the product before. However, with proper storage, the product is possibly edible for up to an additional day.
Sell-by dates are dates that the store should sell the product before. The manufacturer prints such dates on the product, and using a product beyond its sell-by date is not advisable. A pull date is similar in that it tells a vendor when to pull a product from the sales floor. A packing date refers to the date when the manufacturer or the vendor packed the item for sale to the customer. These dates often follow normal dating format, with the month, day and year clearly displayed.