The autumn equinox is the second of two days a year when the hours of daylight and dark are almost equal. In Japan, the Holiday Law defines Autumn Equinox holiday to be a day for people to “respect their ancestors and remember the deceased.” This definition stems from Buddhist tradition, in which the week including the three days before and after the equinox are a time for people to worship their ancestors and pay respects to the family graves. “Equinox” is a term used in astronomy to refer to the two times a year when the sun’s path crosses the plane of the earth’s equator. This occurs once in spring, and once in fall. The autumn equinox marks the beginning of the fall season. Because our calendar does not quite match the solar year, but has to be adjusted every four years with a leap year, the autumn equinox does not fall on the same day every year. Autumn Equinox Day of a given year is decided according to the calendar presented by the National Astronomical Observatory in February of the previous year. Autumnal Equinox Days are usually around September 22nd.