This paper reports findings from a study of Portuguese primary children's understanding of time and historical time. The research involved two classes (first grade, with 24 students aged 6 to 7, and third grade, with 25 students aged 8 to 9) of primary school students during two school academic years in an urban primary school in northern Portugal. The main aim of the study was to analyse how students from the first to fourth grade of education develop chronological (time) concepts and historical understanding. Different data collection techniques and methodologies were used that allowed for three types of triangulation. Data were collected through semi-structured interviews, open interviews, participant researcher observation, audio data, field notes and class diaries. The research was undertaken by the researcher and the class teacher. The research was carried out though a longitudinal study over two years. At three times during the study, the students were asked to arrange historical pictures in chronological order and to explain their sequences. The research data were analysed using a deductive approach. This allowed the construction of a conceptualization system with parameters, categories and subcategories. The findings suggest that temporal understanding and historical thinking are developed gradually but, significantly, they can be facilitated and accelerated by means of specific social studies/history teaching strategies and pedagogy – that is, an intervention strategy.