The dominant mental timelines of native Chinese speakers (Exp1) and Mandarin learners of near-native proficiency (Exp2) was examined with the spontaneous gesture task. The results demonstrated that (1) both groups produced horizontal, vertical, sagittal, fused horizontal and vertical, and fused horizontal and sagittal gestures for all kinds of Chinese temporal words, indicating a strong preference for horizontal over vertical gestures. (2) Negligible correlations between immediate spatio-temporal metaphors and the mental timelines were observed, with an almost non-existent difference in gesture distribution across metaphorical types between the two groups. The findings indicate that (1) the horizontal mental timeline is the dominant timeline for two groups; (2) visuospatial experience exerts a greater influence on temporal cognition; (3) mental timelines formed by the long-term effects of language may operate beyond the immediate metaphors, similar to the horizontal gestures. A unified model proposing embodied experience as the mechanism for activating mental timelines is presented.