Most of the currently standing ones atre from the 19th and the first half of the 20th century. Some are here from medieval times or earlier. In the Neolithic period, this kind of building was a house, then gradually became a small shelter in the field or a tool shed. Can't tell you how old are the kazuns shown in this post. Since they are often part of the walls and don't require much time and resources to build (stones here abound), they were built and destroyed as the borders of the fields and properties were changing.