from wikipedia: The Saturn Return is an astrological phenomenon that occurs at the ages of 27-30, 58-60, and finally from 86-88, coinciding with the time it takes the planet Saturn to make one orbit around the sun. It is believed by astrologers that as Saturn “returns” to the degree in which it occupied at the time of birth — approximately every 29.5 years — a person crosses over a major threshold and into the next stage of life. With the first Saturn Return, a person leaves youth behind and enters adulthood. With the second Return, maturity. And the third and usually final Return, a person enters wise old age.
The first Saturn Return is famous because it represents the first test of character and the structures a person has built their lives upon. According to traditions, should these structures be unsound or that a person is living out of touch with his or her true values, the Saturn Return will be a time of upheaval and limitations as Saturn forces him or her to jettison old concepts and worn out patterns of living. It is not uncommon for relationships and jobs to end during this time of life restructuring and reevaluation.
But the Saturn Return is not all about painful endings. During this time astrologers note that goals are consolidated and people tend to gain a better vision of where they are going in life. There are added responsibilities and a person may reap the rewards from his or her hard work. Many major life milestones seem to happen around the ages of 29 and 30. This is why astrologers believe that the thirtieth birthday is such a major rite of passage because it marks the true beginning of adulthood, self-evaluation, independence, ambition, and self actualization.