When does the Age of Aquarius begin? And what is the Age of Aquarius? The Age of Aquarius is not part of astronomy. It's an astrological age , which occurs because of a real motion of Earth known as the precession of the equinoxes , which, for example, causes the identity of the pole star to change over time . The cycle of precession lasts 25,800 years, and there are 12 constellations of the Zodiac . So, roughly every 2,150 years, the sun's position at the time of the March, or vernal, equinox moves in front of a new Zodiac constellation. The Age of Aquarius begins when the March equinox point moves out of the constellation Pisces and into the constellation Aquarius. When will that be? There's no definitive answer. Various interpretations give different answers to this often-asked question. Age of Aquarius from astronomical perspective. First of all, we give the answer from an astronomical point of view. The International Astronomical Union (IAU) -- which in the 20th century assumed the duty of officially naming and defining all things astronomical -- created official constellation boundaries in 1930. From the perspective of astronomy, then, the beginning of the Age of Aquarius is based upon IAU constellation boundaries, which astrologers or New Age practitioners might or might not choose to use in their computations. According to the Belgian astronomer and mathematical wizard Jean Meeus ( bio here ), who does adhere to the IAU's definitions, the sun at the March equinox passed