Across different domains the magnitude of a stimulus is positively correlated with its perceived duration: bigger, brighter or louder stimuli are usually perceived to last longer than smaller, dimmer or softer ones. According to A Theory of Magnitude (ATOM), temporal and nontemporal magnitudes are linked in the human mind by virtue of sharing a common metric. This claim has been challenged by studies in the domains of brightness and loudness suggesting that it is not the difference in magnitude between stimuli, but rather their degree of change from background that modulates duration judgments. But do the same relationships hold between perceived duration and all prothetic dimensions? We tested the influence of stimulus magnitude and relative change on temporal judgment in the domain of space. We found that, unlike brightness and loudness, spatial length can influence duration judgments independently of the degree of change from a common background, and that this effect is context dependent. Thus, an approach based exclusively on the degree of change between stimulus and background is not sufficient to account for the effect of magnitude on temporal judgments. Our results suggest that space has a privileged link with temporal representations compared to other prothetic domains, challenging the hypothesis that space-time relationships are the product of a domain-general magnitude system.