I am admitting my previous ignorance of the equilux. I always thought that the equinox is the day when there are equal hours of day and night, but I was wrong. So apologies to those who are already well aware, but here's an explanation of the equilux.
I didn't know about equilux tsc so thanks for this. Was talking about it to a friend today who told me 'lux' means light in Latin - as noctis/nox means night (I think I did know that) - same root as nocturnal. I'm afraid along with many other things, I didn't learn Latin at school.