Tropical and Sidereal: What the Ayanamsha Is, and Why Your Newspaper Sign Differs

At the same moment a Western astrologer may place the Sun in Aries and a Vedic astrologer in Pisces. Both are right: they start the zodiac from different points. The gap between the two starting points is the ayanamsha.

Two zodiacs

Tropical: Aries begins where the Sun stands at the spring equinox (20 or 21 March), when day and night are equal. It is tied to the seasons. Western astrology and newspaper horoscopes use it.

Sidereal: signs are counted against the fixed stars. Vedic astrology, the panjika and every nakshatra calculation use it.

Where the gap comes from

The earth's axis wobbles very slowly, like a spinning top. As a result the equinox point slides back against the stars by about 50.3 arc-seconds a year: one degree in about 72 years, a full circle in about 26,000 years. This is precession.

By the Lahiri reckoning the two zodiacs coincided late in the third century CE, around the year 285. The gap has grown since, and in 2026 it stands at about 24°14′ (Lahiri). In other words every planet is about 24 degrees behind in the sidereal reckoning.

What it means for your sign

A sign is 30 degrees and the gap is 24, so for most people the sidereal sign is one sign earlier than the tropical one. Someone who is a "Leo" in the newspaper is very likely a Cancer in Vedic terms. Only those whose Sun or Moon falls in the last six degrees of a tropical sign keep the same sign in both systems.

That is why Suvolagna never prints date ranges such as "21 March to 20 April" beside a sign.

Which ayanamsha is right

Nobody disputes the rate of precession; the argument is about the year the two zodiacs coincided. The main options:

In 1955 the Indian government's Calendar Reform Committee, chaired by Meghnad Saha, recommended fixing the star Chitra (Spica) at exactly 180 degrees from the start of the zodiac, which gave the Lahiri ayanamsha. It has been the standard since. All of Suvolagna's calculations use Lahiri.

Why sankranti and the seasons drift apart

Makar Sankranti now falls around 14 January, while the shortest day (the start of the northward course) is 21 or 22 December. Makar Sankranti is a sidereal event and the solstice a tropical one; about seventeen hundred years ago they fell on the same day. For the same reason the Bengali new year comes about 24 days after the spring equinox.