Progressed synastry starts with two independent clocks
Secondary progressions map one ephemeris day after birth to one tropical year of life. Partner progressions apply that mapping separately to both people. A shared calendar date does not produce one shared symbolic chart: Person A’s elapsed age selects one symbolic moment after Person A’s birth, while Person B’s age selects another after Person B’s birth. The two calculated planet sets can then be compared with each other or with either natal set.
This distinction matters because “progressed synastry” can refer to several overlays. A page that gives only one undifferentiated list can make it impossible to tell whether a row compares two moving planets, one moving planet with the other birth chart, or two natal planets. The calculator labels every row by layer and retains the natal baseline beside the moving results.
The four comparison layers
Progressed A × Progressed B
Both planet sets come from their respective symbolic ephemeris dates. This layer changes as the comparison date changes. Slow outer planets may remain close to their natal degrees, while the progressed Moon moves much faster through the zodiac. The table shows geometry between two derived charts; it does not describe a physical sky on the life date.
Progressed A × Natal B
Person A’s progressed planets move against Person B’s fixed natal longitudes. Direction matters. A row here describes A’s changing derived position relative to B’s birth position. Reversing the pair creates a separate calculation rather than a duplicate label.
Natal A × Progressed B
Person A’s birth positions remain fixed while Person B’s progressed planets move. This layer may contain a contact absent from the previous one because the two people have different symbolic dates and planetary motions.
Natal A × Natal B
The baseline is ordinary natal synastry. It does not change with the comparison date. Keeping it visible makes it possible to check whether a progressed contact repeats a similar natal relationship or introduces different geometry. The calculator does not assign extra weight when a pattern repeats; it simply exposes the measurements.
Worked calculation from life date to symbolic date
Take a birth at 12:00 UTC on 15 June 1990 and a comparison date at 12:00 UTC on 22 September 2026. The elapsed interval is divided by the mean tropical year of 365.24219 days. The resulting age is about 36.27 years, so the symbolic chart is calculated about 36.27 days after the birth moment, in late July 1990.
A second person born in March 1992 reaches a different age on the same September 2026 date and therefore maps to a different symbolic date. The calculator prints both ages and both symbolic UTC moments above the chart. Rounding them to one shared date would erase the independent day-for-a-year calculation.
Read aspects without turning them into a score
The calculator searches conjunctions, sextiles, squares, trines, and oppositions between Sun-through-Pluto positions. It measures the shortest zodiac separation and subtracts the exact aspect angle; the remaining difference is the orb. A one-degree setting includes a 119.4° separation as a trine with a 0.6° orb. It excludes a 117.8° separation because its 2.2° orb is wider than the selection.
The four contact totals are not a rating. A chart with more rows can simply have a wider orb or a temporary cluster. The aspect names describe angles, while supportive, difficult, intimate, or predictive meanings belong to interpretive traditions. Use the exact planets, direction, layer, and orb before any broader reading.
Why the tool omits progressed angles and houses
Progressed planets can be calculated directly from the symbolic ephemeris moment, but angles and houses introduce additional choices. Methods may advance sidereal time, use a solar key, recalculate an apparent chart for the symbolic day, or direct the natal angles. A chart that silently mixes one option with planetary progressions would look more complete while hiding a consequential assumption. The partner tool therefore compares planets only.
Birth time still matters. It fixes the natal UTC moment, the fractional age, and the symbolic time of day; it also improves the Moon position. If a time is unknown, a separate sensitivity analysis is more honest than entering noon as though it were recorded.
Progressed synastry and progressed composites answer different questions
Partner progressions retain two separate people and compare their positions across chart layers. A progressed composite instead calculates a derived relationship chart by taking midpoints between corresponding progressed positions, with further choices for angles and houses. One is an overlay; the other is a constructed third chart. Use the progressed composite and both progressed charts page when the composite itself is the subject.
A practical reading order
- Verify both birth dates, local times, and historical UTC offsets.
- Open the natal baseline and note the exact planets and orbs rather than a total count.
- Inspect both directional progressed-to-natal layers.
- Check progressed-to-progressed contacts separately.
- Move the comparison date and observe which rows persist, enter the orb, or leave it.
- Return decisions about the relationship to direct communication, conduct, and consent.
Calculate the four partner-progression layers.
Calculation details and limits
- Astronomy Engine JavaScript documentation ↗ describes the planetary position library used by the local chart engine.
- Secondary progressions guide explains the site’s tropical-year and symbolic-day calculation.
- Natal synastry calculator supplies the unchanged two-chart baseline used here.