I'm trying to find good, relatively unbiased sources of information on how to interpret the various dates we find on packaged or canned foods, medicines, etc.

Some people I deal with in an in-home caregiver setting are overzealous when it comes to throwing food (and vitamins, etc.) away. Part of that seems to stem from their comprehension of English being only marginal, but part of it seems to be a more widespread confusion about what the various dates mean.

Sometimes their misunderstanding is so severe that they want to throw out an unopened carton of yogurt or package of cheese on Sept. 5 because the "sell-by" date on the carton says "Sept. 4."   They think that's an expiration date and that the product is unsafe the following day. I've also known some of these folks to throw out an unopened package of dried pasta because it was a few months old. As unnecessary as this may be, it would not matter that much if it were their own food (money) they were discarding, but the woman they (we) are working for does not like her food being wasted just because someone is overly cautious or does not understand what those dates mean.

I would like to find some concise, easy-to-read definitions and explanations of terms such as "sell by," "packed on," "best by," "use by," "expires on," etc.    Sometimes info given from the manufacturers errs in the direction of overcaution, partly because they would of course love to sell more product.   And both the manufacturers and some governmental agencies (e.g., Dept of Health) may tend toward overcaution for fear of liability* or just plain 'regulation-gone-rampant'. (E.g., I've known Depts of Health in some locales to require restaurants to throw out still-wrapped packages of crackers in the containers on tables, whether there's any reason to think they've been touched or not, whenever the table is cleared for new customers.   And public schools in the US no longer allow people to bring home-baked goods to share, for "health and safety reasons.")

What I'm looking for is information that's tied to common sense, as well a scientific info, and that weighs the value of not being wasteful as well as the value of safety.

Here are some of the things I've been told by such people as physicians, pharmacists, nutritionists, and others who are in the know about food and drug safety:

Sell-by date:   
The primary reason for this is to facilitate stores' rotation of stock.   In and of itself, it says little about whether or to what extent the product is safe or nutritionally valuable. Some products, e.g., milk, generally "last" 5 to 7 days if properly refrigerated (longer if unopened than after opening). Others, e.g., cheese, may last weeks. Canned goods may last 1 to 10 years, depending on what kind of food it is and the storage conditions.   So much depends on what type of food and how it's stored (temp., humidity).

Stores often mark down or throw out products at or shortly before the "sell by" date, sometimes by state law, but consumers may actually use them long after that.

Packed-on date:
Many canned goods are stamped with the date on which they were packed. Obviously, if that date were misconstrued as an "expiration date," a helluva lot of food would be wasted.

Best-by date:
This is supposed to mean some combination of "tastes best," "has most nutritional value," and "is safest to consume," but in most cases it does not mean the product is worthless or dangerous a few weeks (maybe even months) after that date.    A lot of the time, it means a product (e.g., packaged mac and cheese) will taste best if used by that date. But the food could be consumed long after that date with no ill effects on health.

Use-by date:
This one is supposed to be a strong recommendation to use the product, if possible, by that date, and it seems to mean that the nutritional value and/or safety of the product may deteriorate fairly soon after that date. But safety is much less an issue with some kinds of food (e.g., dried rice or pasta) than others (e.g., meat).

Expiration date:
For medicines, this is supposed to mean you'd better use it by that date or it may be either unsafe or ineffective.   But physicians that I know tell me that some meds (e.g., aspirin) may become dangerous if they're too old, others (e.g., antibiotics) lose potency after a while, and others (e.g., guafenicine or antihistamines) may be quite usable for months, even a year or two after the expiration date.   What's confusing is that the same term is used for those various kinds of products.

My concern, re the work situation, is that just my say-so probably won't convince those who are toss-it-out happy; I need authoritative sources on what these terms mean.

Naturally, I'd also like to refine and expand my own understanding of when it's safe to use a food or medicine product beyond a specified product date and when it's really wise to discard it.

PS:
One thing that some people ignore is that instructions re some of these dates say "use OR FREEZE by" ... .    Of course, if the product has been stored improperly, it may "go bad" long before the "expiration date," too.

Anyway, I'd like to hear your thoughts on these issues, as well as finding some really good consumer-oriented sources.