Solstices and equinoxes. Computer artwork showing the apparent path of the sun in the sky as seen from the Earth's southern hemisphere at different times of the year. The summer and winter solstices occur when the sun appears at noon at its highest and lowest altitudes above the horizon respectively. The equinoxes occur twice a year (around 20th March and 22nd September). At an equinox the Sun is at one of two opposite points on the celestial sphere where the celestial equator and ecliptic intersect. These points of intersection are called equinoctial points.