what is the date of the autumnal equinox
Equinox An equinox is commonly regarded as the moment in which the plane of Earth's equator passes through the center of the Sun's disk,[2] which occurs twice each year, around 20 March and 23 September. This simplified, but incorrect, understanding of Earth's orbital motion can lead to errors of up to 69 seconds from the actual time of equinox.
Winter In the UK, meteorologists consider winter to be the three coldest months of December, January and February.[18] In Scandinavia, winter in one tradition begins on 14 October and ends on the last day of February.[19] In Russia, currently calendar winter starts on 1 December and lasts through to the end of February, though traditionally it was reckoned from the Christmas (25 December in Julian calendar, or 7 January in Gregorian) until the Annunciation (25 March in Julian).[20] In many countries in the Southern Hemisphere, including Australia,[21][22] New Zealand and South Africa, winter begins on 1 June and ends on 31 August. In Celtic nations such as Ireland (using the Irish calendar) and in Scandinavia, the winter solstice is traditionally considered as midwinter, with the winter season beginning 1 November, on All Hallows, or Samhain. Winter ends and spring begins on Imbolc, or Candlemas, which is 1 or 2 February. This system of seasons is based on the length of days exclusively. (The three-month period of the shortest days and weakest solar radiation occurs during November, December and January in the Northern Hemisphere and May, June and July in the Southern Hemisphere.)