Here's a quiz. Let's say you have a bottle of whiskey that says "Distilled June 12, 1996 and Bottled December 5, 2015." How old is the whiskey in that bottle?
The answer is: you don't know. The label has not given you enough information to determine the age of the whiskey. How so? Well, the age of a whiskey is the time spent in a barrel. According to the Federal regulations, Age means:
The period during which, after distillation and before bottling, distilled spirits have been stored in oak containers. “Age” for bourbon whisky, rye whisky, wheat whisky, malt whisky, or rye malt whisky, and straight whiskies other than straight corn whisky, means the period the whisky has been stored in charred new oak containers. [27 CFR §5.11]Even if you know when a whiskey was distilled and when it was bottled, you don't know how much time it actually spent in the barrel. It is not uncommon for whiskeys to be transferred to stainless steel containers before being bottled, sometimes for years. Some brandies spend decades in glass containers. Steel and glass are considered neutral containers that don't impact the flavor of the spirit. While some would certainly argue with that statement, I doubt anyone would argue that their impact in anywhere near as strong as that of an oak barrel.
In contrast to a vintage date or distilled and bottled dates, an age statement (e.g. "10 years old") means that the whiskey was actually in the barrel (and the proper type of barrel) for the amount of time listed. On brandies, however, even those age statements are often incorrect, but that's a story for another post.
The moral of the story is: unless there is an actual age statement on that whiskey, you don't know how old it is.