Either of two times of the year when the sun is at its greatest distance from the celestial equator.
December 21, 2013 @ 09:11 am (PST)
June 21, 2014 @ 03:51 am (Pacific Standard Time)
The summer solstice is the longest day of the year and the winter solstice is the shortest. The summer solstice in the Northern Hemisphere occurs about June 21. The summer solstice occurs in June in the Northern Hemisphere north of the Tropic of Cancer (23°26'N) and in December in the Southern Hemisphere south of the Tropic of Capricorn (23°26'S). The Sun reaches its highest position in the sky on the day of the summer solstice. However, between the Tropic of Cancer and the Tropic of Capricorn, the highest sun position does not occur at the summer solstice, since the sun reaches the zenith here and it does so at different times of the year depending on the latitude of the observer. Depending on the shift of the calendar, the summer solstice occurs sometime between December 21 and December 22 each year in the Southern Hemisphere, and between June 20 and June 21 in the Northern Hemisphere. the winter solstice occurs about December 21, when the sun is over the tropic of Capricorn.The winter solstice occurs exactly when the axial tilt of a planet is farthest away from the Sun, depending on the polar hemisphere of reference. Earth's maximum axial tilt to our Sun during a solstice is 23° 26'. More evidently from high latitudes, a hemisphere's winter solstice occurs on the shortest day and longest night of the year, when the sun's daily maximum position in the sky is the lowest. Since the winter solstice lasts only a moment in time, other terms are often used for the day on which it occurs, such as midwinter, the longest night or the first day of winter. The seasonal significance of the winter solstice is in the reversal of the gradual lengthening of nights and shortening of days. Depending on the shift of the calendar, the winter solstice usually occurs on December 21 or 22 each year in the Northern Hemisphere, and June 20 or 21 in the Southern Hemisphere
September 22, 2013 @ 13:44 pm (PST)
March 20, 2014 @ 09:57 am (Pacific Standard Time)
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day have approximately equal length. At an equinox, the Sun is at one of two opposite points on the celestial sphere where the celestial equator (i.e. declination 0) and ecliptic intersect. These points of intersection are called equinoctial points: classically, the vernal point and the autumnal point. By extension, the term equinox may denote an equinoctial point. An equinox happens each year at two specific moments in time (rather than two whole days), when there is a location (the subsolar point) on the Earth's equator, where the center of the Sun can be observed to be vertically overhead, occurring around March 20/21 and September 22/23 each year. Although the word equinox is often understood to mean "equal [day and] night," this is not strictly true. For most locations on earth, there are two distinct identifiable days per year when the length of day and night is closest to being equal; those days are referred to as the "equiluxes" to distinguish them from the equinoxes. Equinoxes are points in time, but equiluxes are days. By convention, equiluxes are the days where sunrise and sunset are closest to being exactly 12 hours apart.