The way the Ottomans used clocks down to the end of the nineteenth century conformed to the inner logic of their temporal culture and did not disturb its coherence. However, this fabric of practice and meaning began to change rather dramatically during the nineteenth century, as the Ottoman Empire was increasingly assimilated into the European-dominated global economy, and the project of modern state-building began to gather momentum. In their attempt to attain better surveillance capabilities, and higher levels of regularity and efficiency, various organs of the reforming Ottoman state developed elaborate temporal constructs in which clocks played an increasingly important role. As the reform movement spread beyond the government apparatus over the second half of the nineteenth century, emerging groups of officers, bureaucrats and urban professionals incorporated novel time-related ideas, values and behaviors into their self-consciously ‘modern’ outlook and life-style. Acculturated in the highly regimented environment of schools and barracks, they came to identify efficiency and temporal regularity with progress. Mustering new media, new genres, and new sources of authoritative knowledge, they set out to combat temporal patterns they associated with the old political order. Far from being a mere reflection of processes that unfolded in other fields, Ottoman temporal culture is thus shown to be in itself a major arena in which social groups competed for legitimacy, delineated their identities, and put forward their ideologies; it was a medium through which the very concept of modernity was defined, and alternative visions of modernization were expressed, and challenged.