Periodis is a historical atlas of a new kind. We did not try to show the crucial historical moments but to outline the evolution of the European cultural area. Thus we have drawn with a regular frequency the countries of Europe over the centuries.
History by Periods
History is a continuous string of events among which prominent facts sometimes emerge: wars, conquests, revolutions etc. We can evaluate the influence of these important movements in the course of time, by comparing them to the normal periods, to the "control years" in some way. The Periodis historical Atlas, describes the political status of the European continent at fixed intervals. It therefore represents a list of reference points and permits an appreciation of the real range of important items on the continuation of political changes. Stress is put on the precise drawing of territories at one exact instant defined by an arbitrary periodicity, that is the first day of each centennial year.
The notions taken into account are legal, literary or linguistic. We noted in English the names of the states as they are known, and we distinguished the sovereign states, the semi-independent entities, the 1st - when existent - and 2nd level administrative divisions. When information was insufficient, usual names of groups or federations of populations only are indicated. The place-names are usually mentioned in local language but, sometimes, alternative forms are used too, in order to allow easier research.
Names
Names of entities mentioned in the Periodis Historical Atlas are those officially used at the considered time. When the latter are not known or when sources are contradictory, we have applied the names mentionned by sources close to the depicted region and to the century of the map. In cases where such information isn't available, a short circumlocution names such an entity. For nomad populations, we have used the names by which those peoples were commonly described in the 20th century.
Borders
According to knowledge existing in the second half of 20th century, only effective borders were drawn. Thus, territories only nominally subjected to a state are inserted in the area of the state ruling effectively. A dotted frame of same color as that of the dominant power surrounds such a territory and its official name is written in dark grey whereas the dominant state name is black. To simplify matters, one can say that borders are lines someone cannot cross without difficulty at the considered century.
Christos Nüssli, 2009-2011