Recent evidence has shown that the mental representation of time is "embodied"-time is expressed via the hands, the eyes, and the whole body. These findings suggest the existence of a manually reflected mental time line running (in Western culture) horizontally from left (past) to right (future) and an ocularly reflected mental time line running from left/down (past) to right/up (future). We addressed the question whether mental time is also reflected interpersonally and investigated whether an avatar's face orientation (left vs. right) would facilitate a subject's temporal processing in relation to the horizontal mental time line. In combination with a left- or right-gazing avatar, we presented a temporal auditory word ("gestern"-yesterday or "morgen"-tomorrow), and our subjects had to manually categorize the word as being either past- or future-related (classic left/right key-press paradigm). The stimulus-response (SR) mapping was either compatible (past word-left hand, future word-right hand) or incompatible (future word-left hand, past word-right hand). Responses were significantly faster in blocks with compatible versus incompatible mapping. Thus, our results provide clear evidence for manually reflected mental time running from left to right, even for temporal auditory words that are free of potential visual (reading direction) confounds. The presented interpersonal cues (avatar head orientation) facilitated the activation of the horizontal mental time line in blocks with incompatible SR-mapping but not in blocks with compatible (standard) mapping. We conclude that interpersonal cues exert weak effects on the spatial representation of mental time and can help to adapt context-specific mappings of temporal concepts.