Molasses does not have an official expiration date and there is some question as to whether it ever goes bad. It is sold instead with a "best before" date, indicating the date at which it may start to lose flavor.
Whether opened or unopened, molasses lasts well for at least a few years with no diminution of smell or taste; some taste tests show that it is still good after 10 years, according to EatByDate. It is safe to use molasses after the "best before" date has passed. Molasses should be stored in a cool, dark place and need only be discarded if it appears moldy or has had a noticeable change in its appearance or aroma.