The proposed research is concerned with an important aspect of autobiographical memory - the ability to remember when events occurred. It seems clear that a memorial record which preserves the temporal continuity of a person's experience is central to intellectual functioning as well as to a coherent view of the self. Yet major theoretical issues concerning temporal memory have not been explored, and systematic empirical studies remain to be carried out. Available data indicate that, while the time of occurrence of events is preserved in memory to some extent, there is substantial inexactness and bias in temporal reports. In the proposed research, we aim to explore and explain observed biases in temporal reports. The studies outlined below emerge from our recent work on the consequences of hierarchical organization in memory in ordered domains, including temporal memory. Time is divided into units of various sizes (hours, days, weeks). When information is inexact at the level of detail required to answer a question, information from larger temporal units may affect estimation, leading to bias in reporting. Preliminary evidence suggests that bias is a consequence of inexactness in memory and increases over time. We have developed two quantitative models which specify ways in which information at different levels of detail is combined in producing temporal reports. We propose to carry out a set of studies which provide systematic information on inexactness and bias in reporting. The immediate goal is to examine if the models fully account for observed bias. Explaining the sources of bias will contribute to our theoretical goal of understanding how temporal information is represented in memory, and of the retrieval and estimation processes involved in answering temporal questions. It may also contribute to the practical problem of developing methods to collect more accurate social and health related data involving temporal reports.