Vedic Astrology was formulated by the ancient Hindu enlightened saints more than 5000 years ago. They were men of wisdom and knew the secrets of creation. The ancient seers had way back then written about the precession of the equinoxes, and has established that stars were fixed objects in the skies. The Zodiac they calculated was from the 1st star on the belt of Aries. They determined that there were 27 astrological constellations, which spread over the Zodiac belt, covering 360 degrees. They also determined that there were 9 planets, which were of Astrological significance which have cosmic energies and which are influencing the earth, including every human being. Thus, each planet controls 3 constellations, making the figure -" 9X3 = 27. Each constellation has a Zodiac belt covering 13.3333 degrees, which multiplied by 27 makes 359.999 degrees = 360.
Thus every sign of the Zodiac was calculated from one star to another, until it covered 360 degrees. Twelve Zodiac divisions were made, each amounting to almost 30 degrees each.
The Hindu Astrologers also mentioned about 2 shadowy planets called Rahu and Ketu. These two are not planets in mass, but have been given the ranks of planets due to their great influence on Earth. Rahu and Ketu are always opposite each other, and are therefore 180 degrees apart. They always move retrograde, compared tp direct motion of the other planets. Thus the 9 planets include Rahu and Ketu. The Vedic Astrology system does not include Uranus, Neptune and Pluto in their list of planets in our solar system because these extra Saturnian planets transit one Zodiac sign in about 30 years, and would move only 3 Zodiac signs in a man's lifetime. So these are not Astrologically significant, at least not for human lives.
The permutation and combination of 9 planets, 27 constellations and 12 Zodiac signs are the basis of calculation of a birth chart. In the Vedic Astrology system, there are up to 60 divisional charts, called the fine tuning charts, which are focussed on specific areas of our lives, for example, career, children, marriage etc. These divisional charts give more precision to the readings. There is always a major period of a planet in operation, the sub period and the inter sub period of other planets in force. The major, sub and inter sub period of 3 different planets vary in their duration. For example, the major period of Saturn is for 19 years. The major period of Sun is for 6 years, for Jupiter it is 16 years and so on.
Now about the dispute of the Zodiac signs. As I mentioned earlier, the ancient Hindu Vedic Astrologers had calculated the precession of the equinoxes, a phenomenon which makes the Earth "tilt' backwards. They also calculated and established the "obliquity of the ecliptic'. There is a celestial equator, and the ecliptic. The celestial equator is the great circle of the celestial sphere, in which the Earth's equator cuts into. The ecliptic is the arc, along which the Sun moves in the skies. The angle at which the ecliptic cuts the celestial sphere is 23 degrees and 26 minutes. Where it cuts on the north side is called the first point of Aries, and the soutern point of cut is called the first point of Libra.
Now these points are relative and keep changing. Because of the precession of the equinoxes, these points of Zodiac have been moving backwards @ 50.3 seconds every year. Consequently, there is a difference of about 22 degrees between the Eastern and the western Zodiacs.
The Hindu Vedic Astrologers calculated the Zodiac signs from stars, which are fixed in the universe. They also applied the corrections for the precession of the equinoxes and other mathemtical corrections. The ancient Hindu Vedic Astronomical calculations were most precise and accurate.
So, as per western astrology, if your Sun is in Scorpio, in all probability, it will actually be in Libra. That difference of 22 degrees will make you Sun go back to Libra! The Hindu calender has always counted the Sun's entry to the Zodiac signs from the 14th of every month, and not 20th, as the western calculations do. Even the months are calculated as the "Solar' months or the "Lunar' months. The dates of any festivals always vary every year, since the calculations are precise, and not on fixed value basis.
All along, the western astrology has always calculated the "Sun signs' on basis of Sun's entry into Vernal equinox, and continued to count the Zodiacs month after month. Now suddenly, they talk of a new Zodiac sign in between Scorpio and Sagittarius? They also talk of a new constellation! Since when did the western calculations consider constellations???