The pivoting circle of illumination off the Equator on an Earth with a zero inclination was something I first saw in Wikipedia 'Seasons' article and it still remains that way -

https://en.wikipedia.org/wiki/Season

This was extended last year by NASA and the APOD website

https://apod.nasa.gov/apod/ap170319.html


Again and again the explanations now term the Equinox as the Sun directly over the Equator when the Equator always presents the same daylight length throughout an orbit.


Another thing which individuals are keen to jump in it that daylight/darkness is not equal on the Equinox and fiddle about with the tiny variations while they completely ignore the Polar day/night cycle where daylight extends beyond 6 months so no, not all parts of the Earth experience a daylight/darkness symmetry.

The recent uptake of the pivoting circle of illumination explanation is alarming, even for this mind accustomed to wayward notions of motions, orientation and so on. Wish I could give people credit for undoing this mess or better still - working towards explaining the proper mechanisms for the Equinox and the seasons but unfortunately not again this year or any other year previously despite the spectacular productive research the mechanism contains.