There are "sell by" dates and there are "use by' dates. Most food processing plants now use the "use by " date on a can since it is much more clear as to when it is good to be consumed. Many factors influence the use by date... the temperature that the goods where stored is the most critical. Canned goods stored exposed to temperature above 80 degrees for prolonged period of time will not "last" as long as those stored at a consistant temp below 75.
Another influence is the PH level of the products stored in the cans, as well as the actual metal content of the cans.
Typically going a few months past will not be a factor, if they have not had much exposure to high temps. A can that has been frozen should never be consumed.
There is the old saying "when in doubt .. throw it out".