Washington, Jan 15 (IANS): Look again, you may be reading somebody else's horoscope for a preview of your day. The astrological positions determined some 2,000 years ago no longer apply as the stars have shifted in the night sky so much that horoscope signs are nearly a month off.

Astrological signs are determined by the position of the Sun relative to certain constellations on a person's day of birth.

"Astrology tells us that the Sun is in one position, whereas astronomy tells us it's in another position," the Christian Science Monitor quoted Joe Rao, space.com's skywatching columnist and a lecturer at New York's Hayden Planetarium, as saying.

The shift is caused by precession, the wobble in the Earth's axis caused by the gravitational attraction of the Moon to the Earth's equator.

Precession popped into the spotlight this week after Minnesota Planetarium Society board member Parke Kunkle told the Minneapolis Star-Tribune about the gap between the astrological and the astronomical view.

"The earliest known astronomer to recognize and assess the movement of precession was Aristarchus of Samos, who lived around 280 B.C.," Rao told LiveScience.

Astronomers say the Earth is like a wobbly top. As it rotates, its axis swings in a circle, pointing in different directions. As the Earth's position shifts, so does our perspective of the night sky.

Rao said: "We take the North Star, Polaris, for granted. It's the star most closely aligned with Earth's North Pole. But back when the pyramids were constructed, the star that aligned with the North Pole wasn't Polaris at all.

"It was a star in the constellation Draco called Thuban. In 12,000 years, Earth's North Star will be Vega, the brightest star in the constellation Lyra.

The complete rotation takes 26,000 years, said Rao. "Everything in the sky is in flux," he said.

Even if the astrological signs were stable, there's no evidence the stars have anything to do with people's day-to-day existence.

One 2006 study published in the journal Personality and Individual Differences used data from more than 15,000 people and found no relationship between date of birth and personality, according to the Monitor.

Astronomers suggest an overhaul in the process of defining horoscope on the basis of one's birth date as the earth's position vis-a-vis the sun and other stars has changed since the astrological signs were determined over 2,000 years ago.

Apart from the existing 12 astrological signs, the experts include a 13th sign Ophiuchus, a formation which the ancient Babylonians discarded because they wanted 12 star signs.

According to astronomers, the "real" dates of all the 12 astrological signs will be altered for about a period of 30 days.

Here are the "real" dates of astrological signs:

Capricorn: Jan 20 to Feb 16.

Aquarius: Feb 16 to March 11.

Pisces: March 11 to April 18.

Aries: April 18 to May 13.

Taurus: May 13 to June 21.

Gemini: June 21 to July 20.

Cancer: July 20 to Aug 10.

Leo: Aug 10 to Sep 16.

Virgo: Sep 16 to Oct 30.

Libra: Oct 30 to Nov 23.

Scorpio: Nov 23 to 29.

Ophiuchus: Nov 29 to Dec 17.

Sagittarius: Dec 17 to Jan 20.