A day for a year
Secondary progression is the oldest predictive technique still in general use, and the rule behind it is a single sentence: each day after birth stands for one year of life. The chart for your thirtieth birthday is the sky as it stood thirty days after you were born.
There is no astronomical justification for that ratio. It is a symbolic correspondence, defended on the grounds that it produces readable results, and it is worth being clear that this is a different kind of claim from the one a transit makes.
What moves and what does not
Because the technique compresses years into days, the fast bodies do almost all the work.
| Body | Movement per year of life |
|---|---|
| Moon | About 13 degrees; a sign every two and a half years |
| Sun | About 1 degree; a sign every thirty years |
| Mercury, Venus | Roughly a degree, less when retrograde |
| Mars | About half a degree |
| Jupiter outward | Almost nothing across a whole lifetime |
That distribution is the technique in miniature. The progressed Moon is the engine, the progressed Sun marks the long chapters, and the outer planets are effectively frozen at their natal positions.
The progressed Moon
The progressed Moon crosses a sign in about two and a half years and completes a full circuit in roughly twenty-eight, which is close enough to the Saturn cycle to be interesting.
Most practitioners read it as the emotional chapter you are currently in: what you need, what you are drawn toward, what the period feels like from inside. It changes sign often enough to be checkable against your own history, which makes it one of the few predictive techniques you can actually test on the past.
That test is worth doing before trusting it forward. Note the dates the progressed Moon changed sign over the last decade and see whether anything shifted.
The progressed Sun
Moving about a degree a year, the progressed Sun changes sign roughly every thirty years, so most people experience two or three changes in a lifetime. Those are read as major chapters rather than events.
The progressed Sun changing sign at thirty-two, for instance, is conventionally read as a shift in what the person is driving at, and it frequently coincides with the period around the first Saturn return, which muddies attribution considerably. Both techniques claim the same years.
What progressions are not
They are not transits. A transit is where a planet actually is; a progression is where a planet was, read on a different clock. The two describe different things and are usually read together rather than instead of one another.
They also do not predict events. Progressions describe internal development, and the tradition is fairly consistent about this: transits for external circumstance, progressions for what is happening inside. That division is convention rather than law, but it is a useful one.
Progressed houses, and the problem with them
The progressed chart has its own ascendant and Midheaven, which move with the progressed date. Whether they mean anything is contested, because the progressed angles depend entirely on the natal birth time being exact.
An error of four minutes in the recorded birth time moves the progressed angles by a degree, which over decades of progression compounds. If your birth time is approximate, read the progressed planets and hold the progressed angles loosely.
Solar arc, the simpler cousin
Solar arc direction takes the distance the progressed Sun has travelled and adds it to every natal position, so the whole chart advances by one figure. The internal geometry survives untouched and new contacts to the angles appear.
It is cruder than secondary progression and easier to work with, and it is the technique of choice for timing when the natal angles are trusted. There is a separate calculator for it on this site.
Common questions
What does a day for a year mean?
Each day after your birth stands for one year of life, so the chart for your thirtieth birthday is the sky thirty days after you were born. It is a symbolic correspondence rather than an astronomical one.
Which part of a progressed chart actually moves?
The Moon, mostly. It covers about thirteen degrees a year and changes sign every two and a half. The Sun moves about a degree a year and the outer planets are effectively frozen.
How is this different from a transit?
A transit is where a planet actually is now. A progression is where a planet was shortly after your birth, read on a slower clock. Transits are usually read for circumstance, progressions for internal development.
Can I check whether progressions work?
Yes, and it is worth doing. Note when your progressed Moon changed sign over the last decade and see whether anything shifted. Few predictive techniques are this easy to test on the past.
Should I trust the progressed houses?
Only if your birth time is exact. The progressed angles depend entirely on it, and a four-minute error compounds across decades of progression.
What is solar arc?
A simpler relative: the whole chart advanced by the distance the progressed Sun has travelled. Aspects between natal bodies survive and new contacts to the angles appear.