The Gregorian calendar is not the only cultural framework tracking the Bull. Ancient agricultural societies synchronized civic time directly to stellar and solar alignments, producing divergent date ranges for Taurus across different traditions.
| Astrological System | Active Calendar Dates | Primary Basis | Primary Cultural Region |
|---|---|---|---|
| Western Tropical | April 20, May 20 | Vernal Equinox alignment (Seasons) | North America, Europe, Latin America |
| Vedic Sidereal (Jyotish) | May 15, June 15 | Observable constellation backdrop (Ayanamsha) | India, South Asia |
| Solar Hijri Calendar | April 21, May 21 (Ordibehesht) | Solar movement from vernal equinox | Iran, Afghanistan |
| Astronomical Constellation | May 14, June 21 | Actual transit of Sun across IAU Taurus boundaries | Modern Observational Astronomy |
The contrast between the Tropical framework and Vedic Sidereal calculations accounts for the bulk of modern confusion. While Western astrologers lock the start of the zodiac to the spring equinox, sidereal calculations correct for axial precession, the slow wobble of Earth's rotational axis over a 25,772-year cycle. This axial drift displaces the visible stars backward relative to our seasonal markers by approximately one degree every 72 years.
