The day is decided at Cabinet meetings based on the booklet called "Calendar and Ephemeris "created by the National Astronomical Observatory of Japan and is announced in an official gazette as of the first weekday in February of the previous year.
国立天文台が作成する『暦象年表』という小冊子に基づいて閣議で決定され、前年2月第1平日付の官報で発表される。