Ophiuchus is the Serpent-Bearer, a man holding a snake that winds across the sky as the constellation Serpens. Rasalhague marks his head; Barnard’s Star, the fastest-moving star in the sky, sits on his shoulder, and Kepler’s supernova of 1604 blazed at his foot. The ecliptic has always run through Ophiuchus, and when the IAU drew the modern boundaries in 1930 it stayed there. The Sun spends nearly three weeks in it every December. It has never been a sign because the Babylonians wanted twelve signs to go with twelve months, and thirteen would not divide.
The dates above are computed for 2026 from the constellation boundaries the International Astronomical Union fixed in 1930. They move by about a day every seventy years, so they are good for a lifetime, and for the particular day you were born the calculator will check the boundary itself.
