Zodiac sign boundaries year by year, 1950 to 2050

Conventions taken

SIGN BOUNDARIES ARE NOT FIXED, AND THAT IS WHY THIS DATASET EXISTS. Almost every Vietnamese site prints a dead boundary such as Aries from 21 March to 19 April, but the real boundary is the moment the sun reaches an exact multiple of 30 degrees of ecliptic longitude, and that moment drifts by more than a day across years because the calendar year does not divide the solar cycle. Anyone born near a boundary is given the wrong sign by a fixed table. Same mechanism as the solar terms: the twelve sign boundaries are the twelve major terms, so this dataset and moc-tiet-khi-1900-2100 share one solver. THE MEASURED ERROR IS 3.2 MINUTES EARLY ON AVERAGE, 14 AT MOST (checked on 27 September 2026 against IMCCE, Paris Observatory, and USNO, see moc-tiet-khi-1900-2100), because the engine's solar model uses a truncated series; the sat_nua_dem column flags the marks where that error can shift the DAY. This is the TROPICAL zodiac used by Western astrology; the SIDEREAL zodiac of Indian astrology is offset by about 24 degrees and gives a different sign.