This article explores an interesting episode in the history of time, health, and modernity: Britain's 1908 and 1909 Daylight Saving Time (DST) Bills. While the original DST scheme was unsuccessful, the discussions surrounding its implementation reveal tensions central to early twentieth century modernity, namely between industrial time and 'natural' bodily rhythms. This article argues that DST was essentially a public health measure aimed at improving the conditions of indoor workers like shop girls and clerks through government regulation of the private time of the labouring classes. Drawing on the extensive evidence provided to two House of Commons Special Committees, this article reveals how DST debates drew together contemporary discussions around sunlight therapy, night work, and the importance of regular sleeping and eating to tackle Britain's endemic urban diseases like consumption and anaemia. I suggest that the idea of bodily rhythms was increasingly important in medical thinking in this period and that the study of rhythmicity points to the potential for incorporating temporality as an analytical category in medical history.