Why are there school holidays in the summer and why did they become a common principle for the organization and predictability of social and family life ? This is the kind of questions one ignores when the discussion of summer holidays is treated only as a matter of “scholastic rhythms” and political will. This article focuses on the 1880-1914 period, when the school holidays calendar, by pitting the educational ideal of Republicans against the tradition of agricultural work, became a matter of intense national concern. Drawing upon the Durkheimian sociology of social temporalities and the sociology of the state understood as a field of struggles, this article analyzes the battle waged by the educational administration, local politicians, the medical profession and the national daily press around the issue of the dates and legitimate use of holidays. The contested process of institution and national homogenization of the summer holidays calendar – during which these holidays increased in duration and moved from the Fall to the Summer – helps account for the historical movement of school enrolment of French society and the practical ways in which official temporal categories structuring social life were created and imposed.