Retrospective duration judgments of naturalistic events depend on memories of event boundaries.

Daily planning and goal-directed behavior rely on accurate judgments of the duration of past experience. However, retrospective duration judgments are often inaccurate. At the same time, our memory of these experiences transforms over time, with memory forgetting being a common occurrence. In this case, whether and how changes in episodic memory impact duration judgments? Here, participants watched videos depicting daily events with clear boundaries segmenting each subevent. Participants then completed recall and duration judgment tasks both immediately and after 7 days. For whole events, results showed that the recall of the event structure, specifically the number of subevents, significantly influenced immediate and delayed duration judgments. In contrast, event content memories, including gist and recalled details, had no major impact on the entire event duration. In contrast, duration judgments of individual subevents depend on the recall of event content, with immediate judgments linked to recalled gist accuracy and detail richness, while delayed judgments tend to average out, with no significant effect from change in recalled details. Together, these results suggest that retrospective duration judgments rely on explicit episodic memory recall, with the type of recall varying depending on the size and complexity of the naturalistic event. While the segmented structure provides a consistent basis for duration judgments of complex events, single subevents without internal boundaries rely more on granular details.