Equinoxes are the days when the sun is directly overhead the equator.
The sun is overhead at the equator at noon, two times in a year, at the two equinoxes.
The two equinoxes when the sun is overhead the equator are the spring equinox and the Fall equinox.
The Spring or vernal equinox occurs on the first day of the spring normally march 20, while the Fall or autumnal equinox occurs on the first day of the fall, which is usually 22 September.
