Health care systems around the globe are currently orienting themselves towards ‘personalized medicine’, a medical care regime aimed at individualizing prevention, diagnosis, and treatment of disease through proliferating amounts and sources of data, including genetic information. In Denmark, national health policies on personalized medicine focus on harnessing the potentials of genomic science and technology to bring knowledge about patient-specific genetic variation into clinical application. A major hope is to improve public health and prevent common diseases by integrating genomic information in health care, yet to act preventively, a temporal path has to be established defining what kind of knowledge to create and to act upon, and when. This paper explores the temporal orderings of medical knowledge in two different areas: health policy and clinical practice. Examining policy papers on personalized medicine issued by Danish governmental and research institutions, and, comparing them with contemporary practices of using genetic information in preventive cardiac health care, we demonstrate that genetic knowledge-making is ordered around two different conceptual views of time: namely the sequential order and the speed with which such knowledge is produced. We argue that the visions of knowledge-making and early intervention through genomic science and technology as conveyed in policy papers on personalized medicine, challenge preexisting practices and understandings of what constitutes timely prevention and actionable knowledge within clinical care. We close the article discussing how prevention through genomics amplifies the significance of the clinical space for public health as a site for sense-making and translation of controversial genetic knowledge.