Feelings of familiarity are not direct products of memory. Although prior experience of a stimulus can produce a feeling of familiarity, that feeling can also be aroused in the absence of prior experience if perceptual processing of the stimulus is fluent (e.g., Whittlesea, Jacoby, & Girard, 1990). This suggests that feelings of familiarity arise through an unconscious inference about the source of processing fluency. The present experiments extend that conclusion. First, they show that a wide variety of feelings about the past are controlled by a fluency heuristic, including feelings about the meaning, pleasantness, duration, and recency of past events. Second, they demonstrate that the attribution process does not rely only on perceptual fluency, but can be influenced even more by the fluency of conceptual processing. Third, they show that although the fluency heuristic itself is simple, people's use of it is highly sophisticated and makes them robustly sensitive to the actual historical status of current events.