This study investigates the effects of the social setting on prospective time estimation, how time is perceived when a task is performed (i) alone, (ii) with a collaborative, or (iii) with a competitive partner. N=90 participants were tested (30 in each condition). Participants performed a concurrent Simon task for three different durations (15, 30 and 45 seconds) which was followed by a time reproduction phase. Results revealed a main effect of social condition. Reproduction ratios in dual conditions were smaller than in the single condition and also smaller in the competitive condition compared to the cooperative condition. The results provide first evidence that social condition affects time estimation: time “flies” when we work together, in particular when we compete with a partner, showing that cognitive and social processes are heavily intertwined.