This study used open-ended interviews and classroom observations to examine the development of children's understanding of historical time in Northern Ireland. Even the youngest made distinctions among past times, and these differentiations became increasingly numerous with age; students also were able to sequence historic time periods with a high degree of accuracy. This categorization and sequencing involved using personal and family experience, historical information learned in and out of school, and assumptions about the nature of change over time. In addition, students had mastered the arithmetical and linguistic conventions for dates and other standardized notations of time, but the accuracy of their attempts to use such systems depended on their recognition of reference points which they associated with specific visual images; these reference points also derived from personal and family experience and historical information learned in and out of school. These findings indicate that students' understanding of historical time depends on their facility with a set of learned and culturally embedded strategies for describing the past. Differences between the students in this study and those described in previous U.S. research further highlight the impact of learning and cultural context on the development of children's understanding of historical time. (EH)