Everyone can easily describe contents on the web, like Wikipedia. Such contents include wrong information or lacked information. Especially there are a lot of inconsistencies of date information, and they are hard to be noticed by humans. To nd out these inconsistencies automatically, we require to estimate the date information of event. We propose a method for estimating the date information of events which whose date expressions such as “2009/2/20”,“the next day”, or “March 4th” are not described explicitly.