The solar cross-quarter days occur midway between the equinoxes and solstices. In the southern hemisphere these dates are reversed. The northern winter solstice occurs around December 21st of each year, and the northern summer solstice occurs around June 21st. At such a point the duration of the day and the night is either longest or shortest. In the southern hemisphere these dates are reversed.Ī solstice occurs when this angle reaches a maximum or a minimum. The northern vernal equinox (that is, the vernal equinox in the northern hemisphere) occurs around March 21st of each year, and the northern autumnal equinox occurs around September 21st. At such a point in the Earth's orbit the length of day and night is equal (or rather, nearly equal, since atmospheric refraction of the Sun's rays affects the actual length). Summer and winter solstices and the solar cross‑quarter days.Īn equinox occurs when the angle formed at the Earth's center between its axis of rotation and the line joining the Earth to the Sun is a right angle. Windows software for calculating the dates and times of vernal and autumnal equinoxes, Equinoxes, solstices and solar cross-quarter days exact dates and times in Gregorian and Julian CalendarsĮquinoxes, Solstices, and Solar Cross‑Quarter Days
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