The "equinoxes" are two points on the map of the stars.
The center of the sun reaches and passes one of them at some moment around
March 21, and the other one at some moment around September 22.
At those moments, the sun is directly overhead some point on the earth's equator, and
every place on earth has roughly equal periods of sun-up and sun-down on that day ...
the only two times in the year when these things happen.
The equinoxes (approximately 21 March & 21 Sept).
Disregarding the effects of atmospheric refraction . . . If you're standing at the north pole, then the sun is up in your sky from March 21 to September 21, and below your horizon from September 21 until March 21.
When the sun reaches either of the equinoxes,on March 21 and September 21 or 22.
The name given to March 21 and September 21 is the "equinox". This is when day and night are nearly equal in length, marking the beginning of spring (vernal equinox) on March 21 and the beginning of autumn (autumnal equinox) on September 21.
As seen from the south pole, the sun rises once, around September 21, and sets once, around March 21, each year.
March 21 and September 21.
From September 21 until March 21.
There is no place on the surface of the earth where the sun never sets. As seen from the North Pole, the sun is above the horizon continuously from March 21 until September 21. As seen from the South Pole, the sun is above the horizon continuously from September 21 until March 21.
That happens at some point on the equator, at a single moment, on two days of the year ... near March 21 and near September 21.
Exactly at the poles, the cycle is very simple and regular. At the north pole, the sun rises on March 21 and sets on September 21. At the south pole, the sun rises on September 21 and sets on March 21. And that's the whole story.
Beginning around September 22 and ending on March 21.
The equinoxes (approximately 21 March & 21 Sept).
No. The sun is directly over the equator once near March 21 and again near September 21.
Disregarding the effects of atmospheric refraction . . . If you're standing at the north pole, then the sun is up in your sky from March 21 to September 21, and below your horizon from September 21 until March 21.
Beginning around September 22 and ending on March 21.
You're describing an Equinox -- either March 21 or September 21.
March 20/21 is the Equinox, when the sun is on a line directly above the equator, and shines equally on the northern and southern hemispheres.There is another Equinox event in September.