With a growing number of minors entering Europe, a ‘grey zone’ of persons under the age of 18 – the legal age of majority which determines access to protection in the European context – has emerged. Based on an ethnography of ‘age evaluation’ practices conducted between 2017 and 2019 in Marseille, this chapter aims at describing and analysing the device of time and waiting, revealed by multiple temporalities involved in social and legal procedures of age evaluation. Waiting for shelter, for obtaining legal administrative status, for school or for professional integration is combined with social and legal timeframes, markers of differentiation and thresholds between childhood and adulthood. The chapter discusses the measure of bone age as a temporal technique of border control, and temporal controversies about measurement. It demonstrates how, and within which limits, tools from biological anthropology and legal medicine convey meaning about the ‘truth of the body,’ and how they establish borders between legal or illegal migrants through assessments of minority.