The zodiac can be divided into three areas. If it is used to describe the human development from birth to death, the signs can be used to mark the age of an individual human being.
Of course it is a very abstract way and it can differ from person to person. But in general there are three phases (primordial, individual, universal) and two major transitions.
Each phase has four signs to it, and the first and fourth sign of each area are the transitions from one phase into another. And are, what I call here, spirit and soul.
The transitions are from pre-individual (primordial) into individual. And then from individual into trans-individual (universal).
Now this individual part takes an important time in a human life. The transition starts at about the age of 14, puberty. And the next transition is about the age of 42, midlife.
The first is to become an independent individual and the second is the find out the connection with the world again.
Transition from Primordial to Individual
The signs that play a role here are cancer and leo. Cancer (primordial soul) can be seen as the symbol of belonging to a family or tribe.
The sign leo (individual spirit) is the symbol of discovering the own individual essence and become independent.
Transition from Individual to Universal
The signs that play a role here are scorpio and sagittarius. Scorpio (individual soul) can be seen as what looks like the battle between good and evil, but is in essence the integration of the shadow.
The sign sagittarius (universal spirit) is the symbol of the discovering of the whole again, but now as a conscious individual.
So the actual individuation process takes place between the age of 14 and 42 very generally spoken, although it can just as easy last longer.
Or maybe someone never really got seperated from his primordial background which makes the whole process even more difficult.