The study analyzes the professional and public activities of historians who participated in debates on the founding of Czechoslovakia and Yugoslavia in 1988, which took place on the occasion of the seventieth anniversary of these events. It focuses on the forms of historiographical discourse in 1918 and at the end of the 1980s, treating the Czechoslovak and Yugoslav cases separately. It then examines how the specific activities of selected Czech, Slovak, Serbian, and Croatian historians reflected broader circumstances that influenced historical representation in both countries in 1918. In this respect, the study takes into account the changing position and perception of two key dates connected with the founding of the Czechoslovak and Yugoslav states – 28 October and 1 December. It makes note of the differences in perceptions of what essence and meaning the year 1918 was to have in Czechoslovak and Yugoslav history, and above all, it examines in detail the ways these aspects were reflected by historians in both socialist states at the end of the 1980s.