Saturday
equinox
There are two days each year when the day and night are of equal duration, known as the equinoxes. The vernal (spring) equinox occurs around March 21st, marking the beginning of spring in the Northern Hemisphere, while the autumnal equinox occurs around September 22nd, marking the beginning of autumn.
The equinox is when, twice each year, day and night are of equal length (about 22 September and 20 March).
Aequabilis (adj) meaning Equal & Nox, Noctis (n, f) meaning Night.
A Hard Days Night Help! Yellow Submarine
Two times
Twice, at the Summer and Winter Solstaces.
The spring and autumn equinoxes, when day is equal to night in both hemispheres.
The Autumn equinox and the Spring equinox .
These are the Vernal [or Spring ] and Winter Equinox . These days differ slightly and should be marked on your calendar.
Spring and fall equinox.
117 earth days is equal to 1 Venus day. (including night time.) Mercury's day is the equivalent to 176 earth days.