Olives last for 1-2 years beyond a "best by" date if unopened. Of course, olives last for a shorter period of time if they are not stored properly. But remember, olives, like a lot of other fruits, usually have a ‘best before date’ and not a ‘use by date’. Because of this distinction, you may safely use olives to compliment your favorite meals even after the ‘best before’ date has lapsed. You can help olives stay fresh longer by storing them unopened in a cupboard where the temperature is always less than 75o F or 24o C.
Once opened, the olives should be kept in the fridge, fully submerged in their liquid. Never store open cans in the fridge, place the olives and their liquid in an airtight jar or plastic container before putting them in the fridge. If olives are kept submerged in their liquid they can last up to a couple of months past their ‘best before’ date.