The brain efficiently organizes massive amounts of memory – for instance, the what, where, and when components of episodic memory - through multiple parallel, domain-specific processes. However, studies suggest that a common conceptual mapping mechanism may code cognitive distances across all domains. We set out to test the hypothesis that both common and unique neural coding of semantic distance (i.e., what), spatial distance (i.e., where), and temporal distance (i.e., when) simultaneously support episodic memory. Using scalp EEG, we first found that all three components commonly showed a positive correlation between cognitive distance and slow theta power (2.5-5 Hz) in parietal channels, reflective of a domain-general process of cognitive mapping. Fast theta power (5-8.5 Hz) specifically represented spatial and temporal distance in occipital and parietal channels, respectively. We also identified a unique correlate of temporal distance coding in frontal/parietal slow theta power during the early retrieval. All of the above neural markers were associated with individual differences in what, where, and when memory accuracy. These results suggest that our ability to accurately distinguish between memories is achieved through an integration of domain-specific and domain-general neurocognitive mechanisms, mediated by theta power. Further studies are needed to identify whole brain correlates of these theta markers, particularly with respect to the hippocampal memory network.