The aim of this chapter is to examine the relations between time perspective and well-being considering two groups with different cultural backgrounds between Turkish and French. Instruments tapping into positive and negative affect, ontological well-being, flourishing, and five types of time perspective were administered to 615 late adolescents ages between 18 and 24 (Mean of age= 20.95, SD= 3.28). In this study, a recently created subjective well-being construct, known as ontological well-being (OWB), was utilized for measuring eudaimonic happiness based on time perspective in a cross-cultural study. Cluster analysis showed that Turkish people had higher levels of positive affect, negative affect, and psychological flourishing compared to French people, but the levels of regret and nothingness were similar in both groups. Differences between clusters in terms of negative affect were mainly driven by differences in ontological well-being (OWB).