Currently date ("use by") labels on food products do not indicate the safety of your food, nor are they regulated.
According to USDA's Food Safety site, the dating of food products are not required by federal law except for infant formula, although expiration dates may be state required. The dates given on other food products are generally suggestions that are recommendations for best flavor quality.
Research on date labeling in the UK by the organization WRAP shows that 45-49 percent of consumers misunderstand the meaning of the date labels, resulting in an enormous amount of prematurely discarded food. WRAP estimates that a full 20 percent of food waste is linked to date labeling confusion, which also means 20 percent more sales for manufacturers recommending those dates.
The goal of sell-by dates is to help stores stock and shelve their goods. Sell-by dates are designed to indicate a product is still fresh enough for a consumer to take it home and keep in their fridge for days or weeks. Most stores discard products as soon as they're past their sell-by dates, ultimately causing more food waste.
The cost of this waste is significant. In American Wasteland, a book that examines the massive quantities of food wasted from farm to fork, an industry expert estimates grocery stores discard $2,300 worth of "out-of-date" food goods each day. The waste continues at home since many consumers also misinterpret this date and discard products with weeks of good shelf life remaining. And all that adds up to a huge amount of wasted resources, with serious impacts to our land, air and water.
On the USDA website, http://www.fsis.usda.gov/factsheets/food_product_dating/index.asp#9, it lists food storage time charts along with helpful tips, in order to better understand how long your food can last.
Source: GreenBiz.com and Fsis.usda.gov
