Sekino, Tatsuki
International Research Center for Japanese Studies. Professor

Basic information for temporal data of Japanese calendar

The resources for Japanese studies often contain temporal information according to the Japanese calendar. The temporal data in catalogs and documents are usually converted into Gregorian calendar, as most computer systems do not accept Japanese calendar dates. However, periods of years and months prior to 1873 (i.e., when the Japanese calendar was lunisolar), are different for Japanese and Gregorian calendars. This may, therefore, cause problems in retrievals and analyses. Moreover, calendar conversion is not easy as Japanese calendar dates are represented using Chinese letters and the Stems-and-Branches.

HuTime project, which studies information analysis of temporal data (, has provided software tools and data to process dates, months, years, and eras of the Japanese Calendar before 1873. The calendar conversion service ( has functions to interpret Japanese calendar date represented by the Chinese letters and the Stems-and-Branches before converting it into dates of Gregorian Calendar. The calendar conversion service ( has functions to interpret complex date representation of the Japanese calendar containing Chinese letters and the Stems-and-Branches, before converting them into dates of Gregorian Calendar. Additionally, Calendar Linked Open Data ( provides resources to use date of the Japanese calendar in the semantic web. These resources are also linked to information about sequences of Japanese eras, leap months, and so on.

In this report, we consider basic data about temporal information for Japanese studies, in addition to introducing software tools and data of the HuTime project.



時間情報を総合的に扱うための技術開発を進めているHuTimeプロジェクト(では、神武天皇元年(紀元前660年)以降の和暦を扱うためのソフトウェアやデータを提供している。暦変換サービス(は、漢数字や干支を含む複雑な和暦の日付表記を自動的に解釈し、西暦に変換したり、ユーザが指定した書式に統一したりする処理を行う。また、暦Linked Open Data(は、セマンティックWebでの和暦の直接利用を可能にし、年号の前後関係、暦月の大小などに関する情報を提供する。