Here is a fairly extensive and generally accepted write-up http://www.webmd.com/a-to-z-guides/features/do-food-expiration-dates-matter
The only federally mandated expiration date in the US is infant formula, but some states do have others especially on dairy. Most of the labeling in the US is through voluntary programs, while some are strictly marketing gimmicks like beer "born on" dates. In general, most of the regulations are metered out by state, not federal rules and can mean slightly different things in different states. For example, milk is generally considered still usable for 5 to 7 days after the labeled date. But that date may be different in different states. In most places, sell by date is in the 21 to 28 day range from pasteurization. Montana though, the rule it 12 days, which would mean on the surface that milk should last an additional week or two past the label date in Montana. Not necessarily though, as in Montana the milk may be allowed to sit in storage for longer before it is pasteurized. Eggs in some states may get a 21 day sell by date while other states are 28 days or more and different states have very different rules on how those eggs are handled. Having been licensed in one state for eggs myself, I can tell you their rules included any egg collected in that state had to be labeled for 28 days from collection, but if the egg was from out of state no labeling laws were applied at all, the egg could be of any age. Yeah, how crazy was that rule? It allowed old eggs from other states to be blindly dumped into that state.
In most states, as long as it has been correctly stored, most food is still fine beyond the label dates, though quality will be dropping more rapidly after that date. Many states do however have regulations stating that items beyond those dates cannot be sold or even donated after the date in some categories of foods even if the food would still be considered good.
