The equinox falls between the 21st and 23rd, depending upon the year. The reason some references show this year's on September 22nd and others show it on the 23rd is because of time zone differences crossing the International Date Line.The Northern Hemisphere marks the autumnal equinox this year on Saturday, September 22, 2018, at exactly 9:54 P.M. EDT.
Ira Agins
Iron Butt Association