Chronos
Secondary Progressions
Each day following your birth symbolically corresponds to a year of life. Enter your birth details to see where your progressed planets stand.
Defaults to today — can be changed to another date.
What is a secondary progression?
Secondary progressions rely on a simple symbolic convention: one ephemeris day after birth represents one year of life. By recalculating the planetary positions for this progressed day, you get a progressed chart — a sky map that never really existed, but is traditionally used to read the inner evolution and maturation of the birth chart, year after year.
Unlike the solar return chart, which is recalculated each year at the real instant of the Sun’s return, the progressed chart evolves very slowly: the slow planets barely move over several decades of life, while the fast planets (Sun, especially the Moon) trace a readable trajectory across a whole lifetime.
How the calculation is done
The engine determines the progressed Julian day by adding to your birth date as many days as completed years up to the target date, then recalculates the position of the ten classical planets at that instant via the Swiss Ephemeris.
It then calculates the progressed lunar phase (the Moon-Sun gap, across the same eight phases as a lunation), then the tight aspects (1° orb) between the five fast progressed planets — Sun, Moon, Mercury, Venus, Mars — and the positions of your birth chart.
Frequently asked questions
- What does "1 day = 1 year" mean in secondary progressions?
- This is the technique's conversion key: the chart calculated for the Nth ephemeris day after birth symbolically represents year N of life. At age 30, for example, the planetary positions are calculated exactly 30 days after the moment of birth — this progressed chart gives a reading of inner maturation for that year.
- Why do only five planets have calculated aspects?
- The calculator shows the tight aspects (1° orb) between the five fast progressed planets — Sun, Moon, Mercury, Venus, Mars — and the positions of your birth chart. Slow planets (Jupiter through Pluto) move too little over a few dozen ephemeris days to form new exact aspects within a human lifetime; they're shown in their progressed position, with no associated aspect.
- Does the calculator give the progressed Ascendant and Midheaven?
- No, deliberately. The calculation method for a progressed Ascendant or Midheaven is subject to several competing conventions in astrology (solar arc progression, daily, etc.), not settled by this site's reference engine. Rather than improvising a convention, the page limits itself to the planets, whose calculation carries no ambiguity.
- What is the progressed lunar phase?
- The angular gap between the progressed Moon and Sun places the cycle on the same eight phases as an ordinary lunation (new Moon, first crescent, through to the last crescent). In secondary progression, this full cycle spans about 29-30 years of life — the phase therefore indicates which broad stage of inner maturation you're in, not the moon of the day.
- Do secondary progressions require a precise birth time?
- A known time refines the position of the fast planets (especially the Moon, which moves quickly), and so the precision of the progressed aspects. Without an exact time, the sign positions remain a good approximation, but the tight aspects (1° orb) lose reliability.