ENThe problem of historical processes periodization is quite debatable in modern historiography. There are many state historical schools’ traditions that because of political conjuncture are trying to make their statehood history more ancient. This article is devoted to the problems of periodization of The Grand Duchy of Lithuania. The authors attempt to change generally accepted chronology of that state formation. Keywords: chronology of Grand Duchy of Lithuania, Union of Lublin, history of Grand Duchy of Lithuania. [From the publication]