What does this calculator actually confirm?
It confirms membership under the displayed rule and inputs. It does not choose an astrological tradition for you. Three bodies in a sign can produce a positive result at three and a negative result at four; both outputs can be correct descriptions of their chosen thresholds.
Use the audit table to answer “do I have a stellium?” before reading an interpretation. This stellium checker keeps sign and house evidence separate. A stellium birth chart calculator cannot repair an uncertain birth record by generating more decimal places.
From clock time to an inspectable planet list
Resolve one UTC instant
The browser's IANA time-zone rules convert the local date and time, including historical daylight-saving rules available in that browser. A repeated or nonexistent clock time is rejected. If you have a verified UTC timestamp, choose UTC and enter that time directly.
Calculate tropical positions
Astronomy Engine 2.1.19 supplies geocentric vectors, transformed to ecliptic longitude of date. The bundled MIT-licensed library runs locally. Sun and Moon are counted alongside the eight other listed bodies; Earth is not included.
Keep houses conditional
Birth mode uses twelve equal 30° houses beginning at the eastern ecliptic-horizon intersection (the Ascendant). This is Equal houses, not Whole Sign or Placidus. A body within 0.15° of a cusp, or changing house in the five-minute sensitivity check, prevents a house verdict. Manual mode instead uses the chart system you identify.
Expose the count
Results show every counted body and qualifying group. Birth-mode longitude spans use the smallest containing arc, including wraparound at 0° Aries. A span describes the group geometrically; it is not a conjunction-orb test.
“Cannot determine” is a distinct result
| Input problem | What this tool does |
|---|---|
| Unknown birth time | Stops the birth calculation. No guessed noon chart and no house conclusion. A full-day sign stability audit is not implemented here. |
| Ambiguous daylight-saving time | Requests a verified UTC time rather than selecting one occurrence. |
| Missing or unverified location | May show time-specific signs, but withholds all house conclusions. |
| Planet near a sign boundary (0.05°) | Marks sign membership unresolved; established groups can still be shown from their known members. |
| House cusp sensitivity or unsupported latitude | Withholds the house verdict, including negative claims. |
The five-minute check is a sensitivity screen, not birth-time rectification or a guarantee against every input error. Browser time-zone histories may differ, especially for old dates; verify historical records when they matter.
Reject “one green result proves a dominant personality”
A successful count does not measure how powerful a planet is, whether a trait is healthy, or what will happen. It also does not establish that the group survives another house system. Keep the output as a short evidence record, then ask what each member contributes.
For example, a Sun–Mercury–Venus group contains identity, processing and relating in an astrological reading. It is not three copies of the Sun. Switching off Venus can remove a three-body label without erasing the relationship questions represented in the original chart.
Take the result to the right guide
Original work on this page: explicit uncertainty gates, separate sign/house evidence, a reproducible fictional demo, and a rule-sensitive audit table. The astronomy library calculates positions; HoroscopeTools supplies the classification and explanation.