There is no requirement for a "Best Before" date on vinegar - along with salt and sugar, it's exempt. The only reason for there being a date on your bottle would be a very slight change of flavour after that time - otherwise, it's qualities will not have been impaired, and it's perfectly safe to use, for pickles or anything else.
By the way, cider vinegar has a unique property. A teaspoonful in a glass of water will quench your thirst after only a couple of mouthfuls, no matter how thirsty you are. It also leaves your mouth feeling fresh and clean. This is unlike straight water, when you can drink a couple of pints, still feel thirsty, and be left with a slimy feel in your mouth. It's something to do with restoring the electrolytic balance in the body, just like expensive energy drinks claim to do.