The sidereal zodiac measures signs against the stars, while the tropical zodiac measures them from the March equinox. Because of precession the two are now about 24°13′ apart (Lahiri ayanamsa), so most moon and sun signs differ by one sign between the two systems.
Positions are calculated from the Moon's and Sun's geocentric ecliptic longitude. The choice of frame is a convention, not an observation: neither zodiac matches the uneven IAU constellation boundaries.
One Moon · two zodiacs
Tropical vs sidereal
Your Vedic moon sign is usually one sign earlier than your Western one. Here is why, where the Moon is in both systems right now, and a calculator for your own sidereal moon sign and nakshatra.
The Moon right now, in both zodiacs
· ayanamsa 24°13′
Tropical Moon
Virgo
20° Virgo 14′
Sidereal Moon (Lahiri)
Simha · Leo
26° Simha (Leo) 00′
The two frames name different signs right now: tropical Virgo, sidereal Leo. They disagree about four-fifths of the time.
Why the two zodiacs disagree
MODELEDBoth zodiacs divide the ecliptic into twelve 30° signs. They start from different places. The tropical zodiac begins at the March equinox, so it stays tied to the seasons. The sidereal zodiac begins at a fixed point among the stars.
Earth’s axis wobbles slowly (precession), so the equinox slides backward along the stars by about 50″ a year. The gap between the two starting points, the ayanamsa, is now 24°13′ and grows by about one degree every 72 years.
The result: a placement in the first 24° of a tropical sign sits in the previous sidereal sign. Only the last 5°46′ of each sign agree.
Find your sidereal moon sign
The Moon moves about 13° a day and changes sign every two to three days, so the time and time zone of birth matter. Your details stay in this browser; nothing is sent or saved.
Sun sign dates in 2026, both zodiacs
Date the Sun enters each sign (UTC). Sidereal entries are the traditional sankranti dates.
| Sign | Tropical begins | Sidereal begins |
|---|---|---|
| Aries | Mar 20 | Apr 14 |
| Taurus | Apr 20 | May 15 |
| Gemini | May 21 | Jun 15 |
| Cancer | Jun 21 | Jul 16 |
| Leo | Jul 22 | Aug 17 |
| Virgo | Aug 23 | Sep 17 |
| Libra | Sep 22 | Oct 17 |
| Scorpio | Oct 23 | Nov 16 |
| Sagittarius | Nov 22 | Dec 16 |
| Capricorn | Dec 21 | Jan 14 |
| Aquarius | Jan 20 | Feb 12 |
| Pisces | Feb 18 | Mar 14 |
Questions
Why is my sidereal sign different from my tropical sign?
The tropical zodiac starts Aries at the March equinox; the sidereal zodiac anchors Aries to the stars. The equinox drifts backward against the stars by about one degree every 72 years (precession), so the two zodiacs are now about 24° apart. A placement in the first 24° of a tropical sign falls in the previous sidereal sign.
What is the Lahiri ayanamsa?
An ayanamsa is the angle between the tropical and sidereal starting points. Lahiri, also called Chitrapaksha, places the star Spica (Chitra) at 0° sidereal Libra. India's Calendar Reform Committee adopted it in 1955, and it is the most widely used ayanamsa in Vedic astrology. Lunologium uses it for every sidereal reading.
Why does birth time matter for a moon sign?
The Moon moves about 13° a day, so it changes sign every two to three days and nakshatra roughly every day. A birth on a day when the Moon changes sign has two possible moon signs. The calculator flags these days when no birth time is given, and shows the readings at the start and end of the day.