How Tertiary Progressions I work
In this traditional symbolic method, one day of ephemeris time stands for a 27.32158218-day period of a person’s life. We count only periods fully elapsed after the sampled birth instant. At month 0, the progressed planets equal the natal sky. After the first completed period, the ephemeris sample is one day after birth; after 100 completed periods, it is 100 days after birth. The result shows the counted period, birth and target UTC instants, symbolic ephemeris instant, and the next boundary.
This follows the stepwise E. H. A target halfway through a life month uses the chart from its last completed boundary; the planets do not glide continuously between two samples. The period is a fixed 27.32158218 days, not a civil calendar month.
Reading the comparison
The inner ring is the natal sky, and the outer ring uses planetary positions at the symbolic ephemeris date. Both rings use the same tropical zodiac. The table prints longitudes and retrograde marks and gives natal house placements when the birth time and location support them. The wheel is an overview; use the table for planets that cluster or overlap.
Progressed Ascendant, Midheaven, and houses have several competing calculation conventions. This tool intentionally lists progressed planets only, and natal houses separately. If the birth time is unknown, it samples local noon and explicitly withholds natal houses and angles. Since that sample is uncertain, the life-month boundary itself may be shifted by hours. Enter the historical UTC offset, including any daylight saving change, for the birth date; the form does not infer it from coordinates.