Solstice
Solstice is an astronomical term regarding the position of the Sun in relation to the celestial equator. It is related to the axial tilt of the planet, and not the Solar apsides (aphelion and perihelion) of the planet, as many people commonly believe. In other words, solstices are artefacts of the Tropical year, not the anomalistic year.Solstices are those moments of the year when the sun reaches its southernmost or northernmost position, at the Celestial Tropic of Capricorn or Celestial Tropic of Cancer, respectively.
The dates of the Winter Solstice and Summer Solstice are reversed for the northern and southern hemispheres.
Solstice festivals were common (and held primacy) in most cultures of the ancient world.
See also: Equinox