We argue that previous research on time devoted to child care has paid insufficient attention to the conceptualization of care time. Three separate problems are evident. First, the conventional focus on explicit activities with children distracts attention from the larger responsibilities of "passive" care, which ranges from time when children are sleeping to time when they are in the same general area but are not engaged in an activity with parents. Second, the empirical analysis of activity time focuses almost exclusively on parents, overlooking the role of relatives such as grandmothers and siblings. Third, the measurement of active care time often ignores the impact of overlaps among both care providers and recipients. Our analysis of the Child Development Supplement of the Panel Study of Income Dynamics sheds light on these three problems and presents new measures of passive and active care time.