I just bought a jar of pesto sauce, I happen to look at the back and noticed the expiration date…L09-273. What on earth does that mean. I hope that doesn’t mean 3-27-09. 
My first inclination would be to say that it’s an ordinal date; that is, the 273rd day of 2009. However, that corresponds to September 30. It may be the date it was jarred, not the date it’s due to expire. I know that’s the system used with eggs.
Nope it says “Best by”. So that means it expired on September 30. EWWWW!
Good thing I asked about this! :rolleyes: <------Nauseous face.
L is the 12th letter of the alphabet and means the 12th month of the year 2009. I would guess the 273 means the day the product was made.
Actually, products that are sealed in cans and jars have two things going for them:
They tend to be products that are not likely to spoil easily if undisturbed, (unlike milk, for example, that will spoil inside its own container);
and they tend to be very conservatively dated. so that a product with a “best by” date of September 30, 2009 that has remained sealed is liable to be quite safe to eat, (and probably with little or no change in taste quality), well into 2010.
I am not exhorting anyone to eat the product, only noting that it is unlikely to be life threatenng, (or even seriously bad tasting), at this point.
Still Tasty has a handy guide to the shelf life of many foodstuffs.
Regarding date codes, many manufacturers have that information available on their web pages. For example, if you want to know when your can of SPAM was manufactured, go here.
In about 1966 a bunch of us found some self heating cans of soup left over from WWII, that made them a good 20 years old.
Naturally we ate them.
Frozen mammoth is supposed to be tasty.
The LDS (Mormons) have food storage guidelines written up somewhere. I will try and look them up but in the meantime I thought I would mention them. Perhaps somehone has a link handily in their bookmarks.
Checked them out… both amusing links.