Autumnal Equinox Day (秋分の日, Shūbun no Hi) is a public holiday in Japan that usually occurs on September 22 or 23, the date of Southward equinox in Japan Standard Time (autumnal equinox can occur on different dates for different timezones). Due to the necessity of recent astronomical measurements, the date of the holiday is not officially declared until February of the previous year. Autumnal Equinox Day became a public holiday on 1948. In 1947 and before, it was the date of Shūki kōreisai ( 秋季皇霊祭), an event relating to Shintoism. Like other holidays, this holiday was repackaged as a non-religious holiday for the sake of separation of religion and state in Japan's postwar constitution.