The article provides an overview of the development of the field of time use studies. It provides an intellectual history charting the various interests that have shaped the growing applications of this broad social indicator. Recent applications, reflected in this special issue, are (a) interpreting the meaning of leisure, time; (b) the social and environmental consequences of affluence; and (c) non-market work, parenting and balance between work and family. New approaches to trends in average leisure time have attempted to interpret the impact of social and technological change on the meaning of leisure. These approaches suggest that the "economic emergence of women" rather than the "IT revolution" has been the more influential trend and that being "busy" may have replaced conspicuous idleness as the signifier of social status. These new forms of social organization in advanced societies have also attracted a great deal of research on children's use of time, parenting and work-family balance. An important new application for time-use information has been in the study of "diseases of affluence", the health consequences of increasing sedentary activities, and over-eating, the environmental consequences of consumerism, all of which leads to the need to reassess the economic significance of activities that occur beyond the market. A special feature of this article is an extensive review of approaches to valuation (in dollars and cents) of the outputs of unpaid (non-market) work. The article provides a framework for what activities it makes sense to value and the current ideas about "best practice" methods of valuation.