Tropical vs. Sidereal Astrology

zodiac astrology
Tanya Antusenok/

Written by Dayva Segal

Published: November 24, 2023

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Because astrology has been around for thousands of years, there are many different approaches, movements, and perspectives on the field. There is even debate over which methods of timekeeping to use.

Tropical and sidereal are two different ways of dividing the Earth’s ecliptic plane into the 12 signs. The ecliptic plane is an invisible and imaginary extension of the plane of the Earth as it rotates around the Sun. As the Earth moves throughout the year, the stars appear to shift around our planet. Over millennia, people studying these movements created meaning in the shifting stars, leading to astrology and the zodiac.

Astronomers use tropical and sidereal systems to track and predict the movements of the stars.

What Is Tropical Astrology?

Natal chart

This is an example of a chart from Western astrology using the tropical system.

Western astrology uses a tropical system for tracking the movement of the stars. In this fixed system, the position of the Sun in each sign always falls on the same day throughout the year. For example, using tropical astrology, the March equinox always coincides with the start of Aries.

In terms of astronomy, the tropical system measures the movement of Earth compared to the sun. A tropical year is the amount of time it takes the Sun to go around the Earth a full 360° and is measured from the equinox. On the equinox, the Sun’s longitude on the ecliptic plane is measured at 0°.

Using the tropical system, a year on Earth is actually 365.24217 days. So, systems that use tropical timekeeping, like the Gregorian calendar system used in the West, must have leap years every four years to make up for the slight overage.

What Are the Benefits and Disadvantages of Using a Tropical System for Astrology?

Most astrologers who follow Western astrology, including modern astrology, and traditional astrology use tropical astrology. Many Western astrology sites and apps follow the tropical system. Tropical astrology is useful in part because it is predictable. Western astrologers are used to it. For example, each sun sign has the same dates each year. People who believe in tropical astrology are more likely to believe that the stars’ correspondence to seasonal changes here on Earth is what affects someone’s astrology chart, not just the stars themselves.

However, some people believe that because tropical astrology does not reflect the current sky, it is not completely true. Others believe that tropical astrology accurately represents the self’s egoic path in life, while sidereal astrology accurately represents one’s spiritual or soul path in life.

What is Sidereal Astrology?

Example of a Vedic Astrology Chart

This is an example of a Vedic astrology chart, which uses sidereal astrology.

Roughly 2,000 years ago, when sidereal and tropical astrology diverged, they were actually the same. However, the Earth’s rotation around the sun is slightly imperfect, resulting in a change of where the constellations appear in the sky by about one degree every 72 years. Sidereal astrology takes this into account, meaning that sidereal astrology reflects the sky as it actually is at this moment.

When using the sidereal system to track time, a year is about 20 minutes and 24.5 seconds longer than a tropical year.

Within sidereal astrology, there are several ways to determine the starting point of the zodiac, 0° Aries. In Vedic astrology, these systems are called ayanamsa. One of the most popular is Lahiri ayanamsa. Using this tradition, Aries always starts exactly 180° opposite the star Spica, or at 0° Libra. This bright star is located between the constellations Virgo and Libra. The Lahiri ayanamsa is the most popular in sidereal astrology, but there are also others. According to the Fagan/Bradley ayanamsa Spica is close to 29° Virgo.

After so much time has passed, sun signs in sidereal astrology are now off from those in tropical astrology by about 25 days.

Tropical Astrology DatesCurrent Sidereal Astrology Dates
AriesMarch 21 – April 20April 15 – May 15
TaurusApril 21 – May 21May 16 – June 15
GeminiMay 22 – June 23June 16 – July 15
CancerJune 24 – July 23July 16 – August 15
LeoJuly 24 – August 23August 16 – September 15
VirgoAugust 24 – September 22September 16 – October 15
LibraSeptember 23 – October 23October 16 – November 15
ScorpioOctober 24 – November 22November 16 – December 15
SagittariusNovember 23 – December 21December 16 – January 14
CapricornDecember 22 – January 19January 15 – February 14
AquariusJanuary 20 – February 18February 15 – March 14
PiscesFebruary 19 – March 20March 15 – April 14

What Are the Benefits and Disadvantages of Using a Sidereal System for Astrology?

Sidereal astrology is primarily used in Vedic astrology. This practice is popular in India. Other names for Vedic astrology include Hindu astrology and Indian astrology. Some people who believe that it is the heavenly bodies themselves that create our personality and destiny, not just traditional timing and seasons, believe that sidereal astrology is more accurate because it reflects the way the constellations appear in the sky right now.

Additionally, some astrologers say that if your western or tropical astrology information does not resonate with you, check your sidereal astrology chart. You may find that it feels more accurate for you.

Which is Better? Sidereal or Tropical Astrology?

Astrological zodiac signs inside of horoscope circle. Illustration of Woman silhouette consulting the stars and moon over the zodiac wheel and milky way background. The power of the universe concept.

Both tropical and sidereal are valuable forms of astrology.

In the astrology community, there is often debate about which is better or more effective: sidereal or tropical astrology. The truth is, neither one is superior. When it comes to all things in astrology, each choice may have a different purpose. For example, some people have very strong opinions on which house system to use to divide an astrology chart into 12 houses.

However, some astrologers suggest that there is not one correct house system to use. These astrologers believe that different house systems have different purposes and use them in different situations.

The same can be true for sidereal and tropical astrology. As previously mentioned, some astrologers believe that tropical astrology represents more of your earthly self and sidereal represents more of your spiritual side. This is because tropical astrology represents an earthlier experience. It connects to the seasons and happenings here on our planet. The sidereal is more reflective of the stars and sky.

Other astrologers believe that either tropical or sidereal astrology is correct. Others may consult both for different reasons at different times.

Table Comparing Sidereal and Tropical Astrology

Tropical AstrologySidereal Astrology
Used InWestern AstrologyVedic Astrology
Based OnThe positions of the stars when the zodiac was invented/fixed dates & seasons on EarthThe position of the stars where they are now, accounting for slight changes over millennia
Start of the Zodiac0° Aries always starts on March 210° Aries currently starts on April 15, this will change over time

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About the Author

Dayva is a writer at A-Z Animals primarily covering astrology, animals, and geography. She has over 12 years of experience as a writer, and graduated from Hofstra University in 2007 with a Bachelor of Science in Music and a Minor in French. She has also completed course work in Core Strengths Coaching, Hypnotherapy, and Technical Communication. Dayva lives in the SF Bay Area with her cute but very shy cat, Tula.

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