One sky, two rulers
Two thousand years ago the two zodiacs agreed. Then precession — a slow wobble in Earth’s axis, one full turn every ~25,800 years — began carrying the seasonal calendar away from the constellations at about one degree every 72 years. Western astrology stayed anchored to the equinoxes (the tropical zodiac); the astrology of India stayed anchored to the stars (the sidereal zodiac). Today they differ by roughly 24°13′ — almost a full sign.
Neither is wrong. The tropical zodiac is a seasonal, symbolic framework refined in the West for two millennia. The sidereal zodiac is the observational frame — where the planets actually stand against the stars tonight — and the one Jyotish (Vedic astrology) runs on. The honest move is to know your chart in both.
Sidereal sign dates — this year
Because of the 24° offset, the Sun enters each sidereal sign about three and a half weeks later than its tropical counterpart. Computed live with the Lahiri ayanāṃśa:
| Sidereal sign | Sun enters | Sun leaves |
|---|
Ingress dates computed with Meeus solar algorithms; they shift by a day or so year to year. Tropical dates are the familiar horoscope-column ones (Aries from ~March 20, etc.).
Did NASA change the zodiac?
No — and NASA has said so directly. The story resurfaces every year from an educational article noting two true facts: the Sun’s path crosses 13 constellations (including Ophiuchus), and the constellations have drifted relative to the seasonal calendar. The drift is precession — exactly what the sidereal zodiac corrects for with the ayanāṃśa. Sidereal astrology still uses 12 equal signs of 30° each; Ophiuchus is a constellation, not a sign, in both systems.
Lahiri or Fagan–Bradley?
Both are sidereal; they differ only in where they pin the zodiac to the stars. Lahiri (Chitra-pakṣa) anchors the star Spica at 0° sidereal Libra and has been the Indian national standard since 1956 — it is what Vedic software and panchangs use. Fagan–Bradley is the anchor of the Western sidereal school, about 0.9° ahead. The difference only changes a Sun sign for births within roughly a day of a cusp — the toggle above lets you check both.
If your sign shifted — now what?
The Sun sign is the doorway, not the destination. In the sidereal frame the Moon outranks the Sun — and beneath the 12 signs sit the 27 nakshatras, lunar mansions that give one of 108 positions instead of one of twelve. From your Moon’s exact nakshatra flows the Vimshottari daśā: a dated, 120-year timeline of planetary periods. That is what the full calculator computes — free, instantly, in your browser.
See your whole sidereal chart
Sun, Moon, and rising — tropical beside sidereal — plus your Moon’s nakshatra and pada, all nine grahas, and your dated mahādaśā timeline. No signup.
Open the Vedic calculator →