In this history about working hours in France during the nineteenth and twentieth centuries, the authors present two highly original theses which go against some established ideas. Their first thesis is that the limitation or reduction of labour hours was not a political, social or economic issue but primarily a question of public health. The authors second thesis is that the movement for shorter hours was never a major demand of the trade unions since absenteeism served to regulate working hours but the policy of national and international institutions. This is a history book which responds to an impassioned issue in recent French political events. Patrick Fridenson is a historian. Bénédicte Reynaud is an economist.