The French normally do not put a year of bottling on the label or do not mention the aging period. It is all dictated by the very strict French laws: the cognac region does use grades on their labels. The most common and well known are:
V.S. (very special) at least three years of aging in wooden casks
V.O. (very old) at least aged four years
VSOP (very superior old pale) at least aged eight years in wood, but the average you will find is between 10 to 15 years old
XO (extra old) has a minimum age of 10 years
But you can also find:
A.C. at least two years old and aged in wood
Napoléon/Extra/Vieille Reserve at least four years old, but most of the time much older. Also mostly top selections of the cellar master
…year… is always a vintage one. Aged long time and bottled in the year mentioned on the label.
Hors d’Age is most of the time a real find. Great and too old to say something about the aging.
Cep d’or, meaning golden grape rank. At least an aging period of 13 years