The French Republican Calendar was perhaps the boldest of all the reforms undertaken in Revolutionary France. Introduced in 1793 and used until 1806, the Calendar not only reformed the weeks and months of the year, but decimalised the hours of the day and dated the year from the beginning of the French Republic. This book not only provides a history of the calendar, but places it in the context of eighteenth-century time-consciousness, arguing that the French were adept at working within several systems of time-keeping, whether that of the Church, civil society, or the rhythms of the seasons. Developments in time-keeping technology and changes in working patterns challenged early-modern temporalities, and the new calendar can also be viewed as a step on the path toward a more modern conception of time. In this context, the creation of the calendar is viewed not just as an aspect of the broader republican programme of social, political and cultural reform, but as a reflection of a broader interest in time and the culmination of several generations' concern with how society should be policed. Matthew Shaw is a curator at the British Library, London.