Sometimes I employ this predictive technique in my practice. More often they represent timing for psychological events rather than external events. For example the progressed Sun moving into the 2nd house heighten your drive to improve financial resources. And for around 30 years this will be your theme of life. The progressed Sun and progressed lunar phrase are useful to judge one’s stage of life.
The fundamental premise of secondary progressions is a simple formula: one day of time equates to the passage of one year of time. So for example if you are interested in timing influences for the 12th year of a person’s life, open your ephemeris to the month of a person’s birth and count down 12 days after birth (the precise calculation method is a bit more complicated than this).
This method suggests that we live through the entirety of our lives in the days after birth. Each day is a mini-encapsulation of a corresponding year of life. The experiences of that day are a preview of that year, slowly revealing the details of a 24-hour period into a 365-day of actualization.
In essence, secondary progressions are the transits that we experience in the first few months of life that will have a progressive effect over the course of our lives. As such, they evoke experiences that have already been imprinted in our childhood memories.