How does for instance the Age of Aquarius come about?

Answer 1

The earth tilts on its axis, which is an imaginary pole from the north to south poles, around which the earth rotates. As the earth moves around the sun, the axial tilt stays parallel to previous positions, giving the seasons. This axial tilt has a slight wobble. As a result, a particular zodiac sign dominates the world for about 2100 years, moving in retrograde. This affects religion, then culture, and then history interpretation. A complete cycle is called a Great Year, lasting about 26000 years. At the moment, it's the transition from the Age of Pisces to the Age of Aquarius.