An equinox in astronomy is that moment in time (not a whole day) when the centre of the Sun can be observed to be directly above the Earth's equator, occurring around March 20 and September 23 each year.

There is either an equinox (autumn and spring) or a solstice (summer and winter) on approximately the 21st day of the last month of every quarter of the calendar year. On a day which has an equinox, the centre of the Sun will spend a nearly equal amount of time above and below the horizon at every location on Earth and night and day will be of nearly the same length. The word equinox derives from the Latin words aequus (equal) and nox (night). In reality, the day is longer than the night at an equinox. Commonly the day is defined as the period that sunlight reaches the ground in the absence of local obstacles. From Earth, the Sun appears as a disc and not a single point of light; so, when the centre of the Sun is below the horizon, the upper edge is visible. Furthermore, the atmosphere refracts light; so, even when the upper limb of the Sun is below the horizon, its rays reach over the horizon to the ground. In sunrise/sunset tables, the assumed semidiameter (apparent radius) of the sun is 16 minutes of arc and the atmospheric refraction is assumed to be 34 minutes of arc. Their combination means that when the upper limb of Sun is on the visible horizon its centre is 50 minutes of arc below the geometric horizon, which is the intersection with the celestial sphere of a horizontal plane through the eye of the observer. These effects together make the day about 14 minutes longer than the night at the equator, and longer still at sites toward the poles. The real equality of day and night only happens at places far enough from the equator to have at least a seasonal difference in daylength of 7 minutes, and occurs a few days towards the winter side of each equinox.

Solstices occur twice a year, when the tilt of the Earth's axis is most orientated toward or away from the Sun, causing the Sun to reach its northernmost and southernmost extremes. The name is derived from the Latin sol (sun) and sistere (to stand still), because at the solstices, the Sun stands still in declination; that is, its apparent movement north or south comes to a standstill.

The term solstice can also be used in a wider sense, as the date (day) that such a passage happens. The solstices, together with the equinoxes, are connected with the seasons. In some languages they are considered to start or separate the seasons; in others they are considered to be centre points (in English, in the Northern hemisphere, for example, the period around the June solstice is known as midsummer, and Midsummer's Day is 24 June, about three days after the solstice itself). Similarly 25 December is the start of the Christmas celebration, which was a Pagan festival in pre-Christian times, and is the day the sun begins to return back to the northern hemisphere.

Gemini is the third astrological sign in the Zodiac, originating from the constellation of Gemini. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Gemini is considered a "masculine", positive (extrovert) sign. It is also considered an air sign, and is one of four mutable signs. Gemini has been closely associated with the planet Mercury and is considered to be ruled by it.

Individuals born when the Sun was in this sign are considered Gemini individuals. Under the tropical zodiac, the Sun is in the sign of Gemini roughly from May 21 to June 21. Under the sidereal zodiac, it is currently there roughly from June 15 to July 15.

Virgo is the sixth astrological sign in the Zodiac, originating from the constellation of Virgo. In western astrology, the sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Virgo is considered a "feminine", negative (introvert) sign. It is also considered an earth sign and is one of four mutable signs. Virgo is ruled by the planet Mercury.

Individuals born when the Sun was in this sign are considered Virgo individuals. Under the tropical zodiac, the Sun is in Virgo roughly from August 23 to September 22. Under the sidereal zodiac, it is currently there roughly from September 17 to October 17.

Virgo is the only zodiac sign represented by a female.

Aries, the ram, is the first astrological sign in the Zodiac, originating from the constellation of Aries. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Aries is considered a "masculine", positive (extrovert) sign. It is also considered a fire sign, and is one of four cardinal signs. Aries is ruled by the planet Mars. Being the first sign in the zodiac, Aries is associated with the astrological 1st house.

Individuals born when the Sun was in this sign are considered Aries individuals. Under the tropical zodiac, the Sun is in Aries roughly from March 21 to April 19, by definition beginning at vernal equinox. Under the sidereal zodiac, it is currently there roughly from April 19 to May 19.

Cancer is the fourth astrological sign in the Zodiac, originating from the constellation of Cancer. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Cancer is considered a yin sign or alternatively feminine or negative sign, meaning it is more introverted. It is considered a water sign, and is one of four cardinal signs. Cancer is ruled by the Moon. Being the fourth sign in the zodiac, Cancer has been associated with the astrological 4th house.

Individuals born when the Sun was in this sign are considered Cancer individuals. Under the tropical zodiac, the Sun is in Cancer roughly from June 21 to July 22 and under the sidereal zodiac, it is currently roughly from July 21 to August 15.

Leo is the fifth astrological sign of the Zodiac, originating from the constellation of Leo. It's found in the eastern sky. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Leo is considered to be a "masculine", positive (extrovert) sign. It is also considered a fire sign and is one of four fixed signs. Leo is ruled by the Sun.

Individuals born when the Sun was in this sign are considered Leo individuals. Under the tropical zodiac, the Sun is in Leo roughly from July 23 to August 22. Under the sidereal zodiac, it is currently there roughly from August 17 to September 16.

Aquarius is the eleventh astrological sign in the Zodiac, originating from the constellation Aquarius. In western astrology, the sign is no longer aligned with the constellation as a result of the precession on the equinoxes. In astrology, Aquarius is considered a "masculine", positive (extrovert) sign. It is also considered an air sign and is one of four fixed signs. Aquarius has been traditionally ruled by the planet Saturn, and, since its discovery, Uranus has been considered a modern ruler of this sign. Being the eleventh sign of the zodiac, Aquarius is associated with the astrological 11th house.

Individuals born when the Sun was in this sign are considered Aquarius individuals. Under the tropical zodiac, the Sun is in Aquarius roughly from January 20 to February 18. Under the sidereal zodiac, it is currently there roughly from February 13 to March 14.

Scorpio is the eighth astrological sign in the Zodiac, originating from the constellation of Scorpius. In western astrology, the sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In Astrology, Scorpio is considered an introvert, "feminine" negative sign. It is also considered a water sign, and is one of four fixed signs.

Individuals born when the Sun was in this sign are considered Scorpio individuals. Under the tropical zodiac, the Sun enters Scorpio around October 23-24 and exits around November 21-22. Under the sidereal zodiac, it is currently there roughly from November 16 through December 15. People born on these juncture dates should have an astrological chart drawn to determine which sign the sun was in at the time of their birth.

Libra is the seventh astrological sign in the Zodiac, originating from the constellation of Libra. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Libra is considered a "masculine", positive (extrovert) sign. It is also considered an air sign and is one of four cardinal signs. Libra is ruled by the planet Venus (Which also rules Taurus). It is governed by the 7th House (House of Love & Relationships).

Individuals born when the Sun was in this sign are considered Libra individuals. Under the tropical zodiac, the Sun enters Libra around September 23 - 24 and exits around October 22 - 23. Under the sidereal zodiac, it ends on November 15.

Libra, (The Scales of Balance), is the only symbol of the zodiac that is inanimate (it is not represented by an animal or person).

Capricorn is the tenth astrological sign in the Zodiac, originating from the constellation of Capricornus. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Capricorn is considered a "feminine", negative sign. It is also considered an earth sign and is one of four cardinal signs. Capricorn is ruled by the planet Saturn. Being the tenth sign of the zodiac, Capricorn has been associated with the astrological 10th house.

Individuals born when the Sun was in this sign are considered Capricorn individuals. Under the tropical zodiac, the Sun is in Capricorn roughly from December 22 to January 19. Under the sidereal zodiac, it is currently there roughly from January 15 to February 12.

Pisces is the twelfth astrological sign in the Zodiac, which originates from the Pisces constellation. In western astrology this sign is no longer aligned with the constellation because of the precession of the equinoxes. Pisces is represented by a pair of fish that are swimming in opposite directions, but remain held together at the tail by a cord. In astrology, Pisces is considered a feminine sign or negative sign. It is also a water sign, and is one of four mutable signs. Being the twelfth sign, Pisces is associated with the astrological 12th house. Pisces has been traditionally ruled by the planet Jupiter, but since its discovery, Neptune has been considered a modern ruler of this sign. Some astrologers mostly use one to the exception of the other, but some consider them to be co-rulers of this sign and essentially use both (see Domicile).

Individuals born when the Sun was in this sign are considered Pisces individuals. Under the tropical zodiac, the Sun is in Pisces roughly from February 19 to March 20, and under the sidereal zodiac, it is currently there roughly from March 15 to April 13.

Taurus is the second astrological sign in the Zodiac, originating from the constellation of Taurus. In western astrology, this sign is no longer aligned with the constellation as a result of the precession of the equinoxes. In astrology, Taurus is considered a "feminine", negative sign. It is also considered an earth sign and is one of four fixed signs. Taurus is ruled by the planet Venus (which also rules Libra). Being the second sign of the zodiac, Taurus has been associated with the astrological second house. The glyph is also the alchemical symbol for rocksalt.

Individuals born when the Sun was in this sign are considered Taurus individuals. Under the tropical zodiac, the Sun is in Taurus from April 20 to May 20. Under the sidereal zodiac, it is currently there roughly from May 15 to June 15. An astrological chart must be plotted to ascertain the exact position of the Sun around these juncture dates.

Sagittarius is the ninth astrological sign in the Zodiac, originating from the constellation of Sagittarius. In western astrology, the sign is no longer aligned with the constellation as a result of the precession of the equinoxes. Sagittarius is classed as a positive or masculine, extrovert sign; its element is fire and its quality is mutable. Sagittarius is ruled by the planet Jupiter.

Individuals born when the sun was in this sign are considered Sagittarius individuals. Under the tropical zodiac, the sun is in Sagittarius roughly from November 22 to December 21. Under the sidereal zodiac, it is currently there roughly from December 16 to January 14.