Temporality is an important characteristic of text documents. While some documents are clearly atemporal, many have temporal character and can be mapped to certain time periods. In this paper, we introduce the problem of estimating focus time of documents. Document focus time is defined as the time to which the content of a document refers to and is considered as a complementary dimension to its creation time or timestamp. We propose several estimators of focus time by utilizing external

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... ge bases such as news article collections which contain explicit temporal references. We then evaluate the effectiveness of our methods on diverse datasets of documents about historical events in five countries.