Developing an effective theory of periodization requires an engagement with the multilayered figurative constructions of historical time made by historians and historical actors. The fin de siècle c1890-1914, a period variously interpreted as reflecting an historical endpoint or an anxious transition to twentieth century modernity, provides a compelling focus for this engagement. John Zammito has argued that ‘[Reinhart] Koselleck’s formal theory of historical time points ultimately to periodization as the fundamental theoretical domain for historical practice’. Koselleck argued that the condition of modern ‘historical time’ stimulated the development of ‘multiple temporalities’, ‘different passages of time which reveal different tempos of change’. This complex dynamic was reflected in the cultural manifestations of the fin de siècle, and the interpretations made by both historical actors and historians of its temporal nature. Following Koselleck, I argue that the fin de siècle may be best understood as a ‘synchronic unit’, a discrete temporal domain within the multiple temporalities of Neuzeit, the new time of modernity.