This paper explores the history of the hour as a unit of labour in the era of the first industrial revolution (ca. 1760-1840) in Britain and the British empire. The history of employment is easy to construe as a history of free workers contracting freely with employers. However, the origins of hourly work show deep connections, both practical and ideological, between free and enslaved labour, as well as the correspondence and personal and commercial connections between British factory owners and slaveholding colonial landowners. The transition from a system of labour based on traditional relationships between landlords and tenants, informally negotiated over years, to a system of shorter-term contracts based on seasonal, monthly, weekly, and eventually hourly work took place against a backdrop of economic crisis, land alienation and war. Experiments with breaking a days’ labour into hourly units began in Britain’s cotton and ceramics factories, where labourers who might otherwise have worked on family farms contracted to sell their work to manufacturers. At the same time, in Britain’s island colonies in the Caribbean, where sugarcane was a virtual monoculture, and in the more economically diversified mainland colonies that became the United States of America after the American Revolution, slaveholders also experimented with dividing the labour of enslaved workers into hours. The hour became a useful mechanism for measuring labour, and for setting production goals for both free and enslaved labourers. The useful unit of an hour of work placed new pressures on workers, free and enslaved, and transformed the kinds of negotiations labourers could engage in, in factories and on plantations. Hourly work became a common touchstone in the lives of both free wage workers and enslaved workers even as classical political economists theorised rigid distinctions between free labour and slave labour.