The equinox is the time of the year when the Sun crosses the plane of Earth’s Equator. The Sun is at its highest point in the sky with respect to the Equator. It stands at its zenith and its declination on the equatorial coordinate system is 0. There are two equinoxes each year, also called equinoctial points since an equinox is a point where the celestial equator and ecliptic (the apparent path of the Sun on the celestial sphere) intersect. The first equinox happens between March 20th and 22nd, the second equinox between September 22nd and 23rd in the northern hemisphere, heralding the beginning of spring and fall, respectively.