Why we publish this
Most astrology platforms ask you to trust their calculations without ever showing how they arrived at them. We think that's backwards — especially for something as personal as your birth chart. This page explains exactly which calculation methods, data sources and AI approach CosmicGPT uses, so you can verify our work instead of just taking our word for it.
How your chart is calculated
Ayanamsa (sidereal correction)
We use Lahiri (Chitrapaksha) ayanamsa — the Indian government’s Rashtriya Panchang standard — calculated fresh for your birth date (not a fixed stale constant). The numeric degree used for your chart is stored with the result for auditability. If you've used a Western astrology app and gotten a different Sun sign here, this offset — not an error — is why.
House system
Primary D1 (Rashi) houses use whole-sign — the traditional Vedic method where each house is exactly one sign from Lagna. The KP module uses Placidus cusps; Bhav Chalit uses Sripati (Bhava Madhya). We state the system per chart type rather than mixing them silently.
Rahu–Ketu (lunar nodes)
Rahu and Ketu default to the Mean Node (constant lunar-node rate). True Node (orbital wobble) is available as an advanced preference but is not the default, because classical Parashari practice and most Indian software use Mean Node.
Ephemeris source
Planetary positions are calculated with astronomy-engine — VSOP87/ELP-derived models aligned with NASA JPL-class orbital data. This means the raw planetary positions in your chart are astronomically verifiable, independent of any astrological interpretation layered on top.
Dasha system
Life-period timing (Mahadasha/Antardasha) is calculated using the Vimshottari Dasha system, based on your Moon's Nakshatra position at birth — the standard timing method in Vedic astrology, spanning a 120-year cycle across nine planetary periods.
Sunrise and the Vedic day
For daily Panchang and muhurta, the Vedic day is bounded by actual sunrise and sunset at the selected place (computed with astronomy-engine), not by midnight and not by an assumed 6:00 AM. Birth-moment Tithi/Nakshatra/Yoga/Karana are still evaluated at the exact birth instant.
Time zone and location handling
Birth civil time is converted to UTC using the IANA time zone database for the place (India cities → Asia/Kolkata), applying the offset that was in effect on that date — including historical transitions present in the OS/runtime tzdata. Note: separate colonial city standards such as Bombay Time vs Madras Time are only as accurate as the IANA zone mapped for the coordinates; we do not invent custom city-time tables beyond IANA. If your city isn’t in our database, we use the nearest verified coordinates and flag this on your chart.
The five silent settings (locked)
Why platforms disagree on identical birth data — our defaults, justification, and documentation:
| Setting | Default | Why |
|---|---|---|
| Ayanamsa variant | Lahiri (Chitrapaksha), date-specific | Indian Astronomical Ephemeris / Rashtriya Panchang standard; recomputed for the birth instant (not a fixed constant). |
| True vs Mean Node (Rahu/Ketu) | Mean Node | Classical Parashari convention; matches most competitor defaults. True node remains experimental on astronomy-engine. |
| House system (per chart type) | D1 whole-sign · KP Placidus · Bhav Chalit Sripati | Parashari traditional whole-sign for primary D1; KP requires Placidus; Sripati for classical cusp (Bhav Chalit) view. |
| Sunrise-based day boundary | Actual local sunrise (astronomy-engine) | Vedic civil day / muhurta / daily Panchang timing starts at sunrise, not midnight or a fixed 6 AM assumption. |
| Historical timezone handling | IANA tz database at birth instant | Civil offsets change over time (e.g. India wartime +06:30, pre-standard LMT). Fixed modern IST would misplace older charts. |
Lal Kitab module
Lal Kitab houses use the same whole-sign D1 houses; Pakka Ghar and Rin are rule tables, not a second ephemeris. The report lists Pakka Ghar status, Andha (Saturn/Rahu/Ketu in 6/8/12), Pitri/Nari/Dev/Maatru Rin screens, and Tier-1 cultural remedies — each with basedOn placements.
Sade Sati tracker
Sade Sati = Saturn transiting the 12th, same, or 2nd sign from natal Moon. Phase windows use Saturn sidereal sign ingress (astronomy-engine + Lahiri). Dhaiya off by default. No fear-% scores — read with dasha context.
Varshphal (Tajika)
Varshphal = solar return (sidereal Sun = natal Sun) + Varsha Lagna + Muntha + simplified Varsheshwara + a small Saham set. An annual timing overlay — not a replacement for the birth chart or Vimshottari.
Prashna Kundli
Prashna = chart for the asking instant/place (Lahiri, whole-sign Lagna). Topic→house map; lean/caution/insufficient from topic lords in kendra/trikona vs 6/8/12/combust/malefic contact — each with basedOn; no %-odds. Not medical or legal verdicts.
Muhurta (electional)
Muhurta Finder = up to 14 days of daytime Choghadiya segments + Panchang. Hard: Rahu Kaal, Vishti. Soft/support via activity profiles. Results are pass / caution / avoid — no luck %. Natal Moon 8th filter optional (off by default). Single-day Choghadiya/Hora/Rahu Kaal tools remain separate.
Birth-time rectification
Sweeps approximate birth time ± window; scores Vimshottari maha/antar lords vs dated event houses. Confidence low/medium/high; score = event-match ratio (not “% true birth time”). Lagna-flip caution; user confirms before applying time to kundli. Heuristic aid — not certificate-grade proof.
What's calculation vs. interpretation vs. contested
We think this distinction matters and most platforms blur it deliberately. Here's how we separate it:
- Calculation (astronomically verifiable): Planetary positions, sign placements, house cusps, Nakshatra, dasha timeline. These come from ephemeris data and math — two correctly-built engines using the same inputs will always agree.
- Traditional interpretation (textually grounded, not verifiable): What a placement "means" — for example, that Mars in the 7th house relates to relationship friction. This comes from classical texts (Brihat Parashara Hora Shastra, Saravali, and others) and centuries of interpretive tradition. It's not astronomically provable, but it isn't invented either — it has a documented lineage, which we try to reference where relevant.
- Contested or school-specific: Different traditions (Parashari vs. Jaimini, Vedic vs. KP, Vedic vs. Western) sometimes disagree on the same chart. Where this happens, we try to show the disagreement rather than silently picking one school and presenting it as the only answer.
How our AI Guru works
Our AI does not generate or invent planetary positions — it only interprets a chart that has already been calculated by our ephemeris engine. When you ask it a question, it:
- Reads your already-calculated chart data (placements, houses, current dasha)
- References the relevant traditional principle for your question
- Explains that principle in plain language, and tells you which placement it's basing the answer on
If a question requires judgment calls that traditional texts disagree on, the AI says so instead of presenting one interpretation as definitive. It does not diagnose health conditions, give financial or legal advice, or predict specific life events with false certainty — astrology here is offered as a traditional framework for reflection, not a guarantee.
Astrologer verification
Astrologers on CosmicGPT are reviewed before being listed, based on documented training or lineage, and years of practice. We show verified experience and specialization clearly on every profile rather than unverifiable star-only ratings.
Data privacy
Your birth details are used only to calculate your chart and are not sold to third parties, including remedy or gemstone sellers. You can request deletion of your birth data at any time via Contact.
Limitations, honestly stated
Astrology, in any tradition, is not a predictive science in the way physics or medicine is. Two competent astrologers can read the same chart differently. We build our tools to be as calculation-accurate as possible and our interpretation content to be traditionally grounded — but the meaning you take from your chart is ultimately a framework for reflection, not a fixed outcome. Important life decisions should be made with full information, not chart guidance alone.
Questions about our methodology
If you have a technical question about how a specific calculation was made, contact us at hello@cosmicgpt.in — we're glad to explain further.
- What ayanamsa does CosmicGPT use?
- Lahiri (Chitrapaksha) ayanamsa — the standard used in India’s Rashtriya Panchang and most Vedic software.
- What’s the difference between Vedic and Western astrology on this site?
- Janam Kundli and most calculators use sidereal Lahiri positions with whole-sign houses. Learn guides also cover Western (tropical) concepts separately and label which system you are reading.
- Does CosmicGPT sell my birth data?
- No. Birth details are used to calculate your chart and are not sold to third parties, including remedy or gemstone sellers. You can request deletion via Contact.
- Does the AI invent planetary positions?
- No. AI Guru only interprets chart data already calculated by the ephemeris engine.