In my previous life within the food industry, I would offer the following opinion. The date on the label is advisory. The contents of cans and jars are cooked to the point of pasteurization at least. So long as the process was complete, they remain sealed and under negative pressure until opened.Hence the slight 'hiss ' when opened, cans expand slightly and jars relax their seal. A visible effect. Damaged, dented tins, rusted inner tin surfaces, jars without that 'vacuum ' effect are suspect and, personally, would be discarded. The nutritional value, vitamins and flavours may well have been compromised or destroyed during the heat process of canning. Hence, not like fresh.
Greater danger from part -consumed foods left too long, possibly cross-contaminated by proximity to raw foods, vegetables, uncooked meats and thumb prints on plates,etc. Thorough reheating reduces most such risk. Hence the ability of 'fast food' outlets to recook prepared ingredients, in super hot woks etc, without major incident. If not done effectively, then epidemics!!
