Celestial longitude in the context of "Fundamental plane (spherical coordinates)"

The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac belt appear the Moon and the brightest planets, along their orbital planes. The zodiac is divided along the ecliptic into 12 equal parts, called "signs", each occupying 30° of celestial longitude. These signs roughly correspond to the astronomical constellations with the following modern names: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.

The signs have been used to determine the time of the year by identifying each sign with the days of the year the Sun is in the respective sign. In Western astrology, and formerly astronomy, the time of each sign is associated with different attributes. The zodiacal system and its angular measurement in 360 sexagesimal degree (°) originated with Babylonian astronomy during the 1st millennium BC, probably during the Achaemenid Empire. It was communicated into Greek astronomy by the 2nd century BC, as well as into developing the Hindu zodiac. Due to the precession of the equinoxes, the time of year that the Sun is in a given constellation has changed since Babylonian times, and the point of March equinox has moved from Aries into Pisces.

Aries (♈︎; Ancient Greek: Κριός, romanized: Kriós, Latin: Ariēs, lit. 'ram') is the first astrological sign in the zodiac, spanning the first 30 degrees of celestial longitude (0°≤ λ <30°), and originates from the Aries constellation. Under the tropical zodiac, the Sun transits this sign from approximately March 21 to April 20 each year. This time-duration is exactly the first month of the Solar Hijri calendar (Arabic: Hamal; Persian: Farvardin; Pashto: Wray).

According to the tropical system of astrology, the Sun enters the sign of Aries when it reaches the March equinox, typically on March 21. Because the Earth takes approximately 365.24 days to go around the Sun, the precise time of the equinox is not the same each year, and generally will occur about six hours later from one year to the next until reset by a leap year. The leap day February 29 causes that year's March equinox to fall about eighteen hours earlier compared with the previous year.

Cancer (♋︎; Ancient Greek: Καρκίνος, romanized: Karkínos, lit. 'crab', Latin for the "Crab") is the fourth astrological sign in the zodiac, originating from the constellation of Cancer. It spans from 90° to 120° celestial longitude. Under the tropical zodiac, the Sun transits this area between approximately June 22 and July 23.

In astrology, Cancer is the cardinal sign of the Water trigon, which is made up of Cancer, Pisces, and Scorpio. It is one of the six negative signs, and its ruling planet is the Moon. Though some depictions of Cancer feature a lobster, crayfish, scarab beetle or a turtle, the sign is most often represented by the crab, based on the Karkinos. Cancer's opposite sign is Capricorn.

Leo (♌︎; Ancient Greek: Λέων, romanized: Léōn, Latin for "lion") is the fifth sign of the zodiac. It corresponds to the constellation Leo and comes after Cancer and before Virgo. The traditional Western zodiac associates Leo with the period between about July 24 and August 23, and the sign spans the 120th to 150th degree of celestial longitude.

Leo is associated with fire, accompanied by Aries and Sagittarius, and its modality is fixed. The constellation Leo is associated with the mythological Nemean lion. The lion is a very important and prominent symbol in Greek mythology.

Libra (♎︎; Ancient Greek: Ζυγός, romanized: Zygós, Latin for "scales") is the seventh astrological sign in the zodiac. It spans 180°–210° celestial longitude. The Sun transits this sign on average between September 24 and October 23. The symbol of the scales is based on the Scales of Justice held by Themis, the Greek personification of divine law and custom. She became the inspiration for modern depictions of Lady Justice. The ruling planet of Libra is Venus along with Taurus. Libra is the only zodiac sign that is represented by an object; the other eleven signs are represented by either an animal or a mythological character though some depictions feature a man holding the scales with his hands.

Capricorn (♑︎; Ancient Greek: Αιγόκερως, romanized: Aigókerōs, Latin for "horned goat") is the tenth astrological sign in the zodiac out of twelve total zodiac signs, originating from the constellation of Capricornus, the goat. It spans the 270–300th degree of the zodiac, corresponding to celestial longitude. Under the tropical zodiac, the sun transits this area from around December 22 to January 20. Capricorn is one of the three earth signs, alongside Virgo and Taurus, a negative sign, and one of the four cardinal signs. Capricorn is ruled by the planet Saturn and its opposite sign is Cancer.

Pisces (♓︎; /ˈpaɪsiːz/; Ancient Greek: Ἰχθύες Ikhthyes, Latin for "fishes") is the twelfth and final astrological sign in the zodiac. It is a mutable sign. It spans 330° to 360° of celestial longitude. Under the tropical zodiac, the sun transits this area between about February 19 and March 20. In classical interpretations, the symbol of the fish is derived from the ichthyocentaurs, who aided Aphrodite when she was born from the sea.

Some tropical astrologers believe the current astrological age is the Age of Pisces, while others maintain that currently it is the Age of Aquarius.