Delirium Nocturnum vintage

[Kickass]

I recently bought a bottle of Delirium Nocturnum from a local retailer. When I pulled back the blue foil I saw the cork was labeled 2008. I’m very interested in aging a some bottles for a few years. My question is this: how can I determine what year a bottle of Delirium Nocturnum is without peeling back the foil in the store?