The life-course perspective provides an orienting framework for identifying the mechanisms that link lives and social structures in historical time. It focuses on the intersection between biography and history. Accordingly, the conceptualization of time is a central concern. Biographical time is defined by the links between chronological age, psychophysical development and/or decline, and successive social statuses. Biographies are variable sequences of social statuses across the life span, with some statuses (but not all) highly correlated with chronological age. Historical time also has chronological and social components, with the latter tied to events or periods that exert differential influences on biographies. Age, period, and cohort are core concepts in the life-course perspective. Briefly defined, age refers to biographical time; period refers to historical time; and cohort refers to a group whose members experience a particular event at the same time in their lives. Persons born at the same time constitute a birth cohort. As they age, they come to encounter historical events from a different social vantage point from other birth cohorts.