Sources and References
The rules and tables in our tools were taken from, or compared with, the texts and reference pages listed here. Where a site was used only for comparison, no text was taken from it. The date shows when we last checked them.
Sources and References
The rules and tables of our tools rest on the sources below. Each source is listed with what it was used for and when we looked at it. Where a site was used only for comparison, its text or tables were not taken.
Calculation engine, data and time
- Don Cross: astronomy-engine (MIT) planetary positions and rise/set
Engine for planet positions and rise and set times (MIT licence). Checked on: 10-10-2026 - Astrodienst: Swiss Ephemeris programmer documentation (Lahiri constants t0=2435553.5 ayan_t0=23.250182778-0.004658035)
Constants of the Lahiri ayanamsa (facts only; none of their code is used). Checked on: 10-10-2026 - GeoNames: Data dumps licence page (cc-by; credit required)
Birth place search data, CC BY 4.0, credited. Checked on: 10-10-2026 - IANA: Time Zone Database (public domain)
Time zone database (public). Checked on: 10-10-2026 - IANA tz database (Paul Eggert repository): tzdb asia file: Zone Asia/Kolkata rules and India history comments
Rules for Asia/Kolkata and the history of Indian time. Checked on: 10-10-2026 - GeoNames: India country file IN.zip, alternatenames/IN.zip, admin1CodesASCII.txt and readme.txt (licence: Creative Commons Attribution 4.0); built into files/cities_in.json
File of Indian cities, CC BY 4.0, credited. Checked on: 13-10-2026 - npm registry and github.com/cosinekitty/astronomy LICENSE: astronomy-engine package metadata: latest version 2.1.19 (published 2023-12-14), licence MIT; LICENSE file on GitHub reads MIT License
Version and licence (MIT) of astronomy-engine checked. Checked on: 13-10-2026
Classical texts
- RoxyAPI: Gun Milan scoring rules (prose; no full tables)
Cross-check of the Guna Milan scoring rule (no text taken). Checked on: 10-10-2026 - Chowkhamba Sanskrit Series Office (Banaras 1948) scan on Internet Archive: Muhurta Chintamani with Maniprabha Hindi commentary (ed. Kapileshwar Shastri) pp.176-179 (leaves n191-n194) and p.341 (leaf n358)
Muhurta Chintamani: Vashya, Yoni and muhurat rules (facts and tables). Checked on: 10-10-2026 - Internet Archive scan (edition data not in metadata): Muhurta Chintamani with Piyushadhara and Pitambara Hindi commentary (Kedar Datt Joshi) pp.331-336 (leaves n384-n388)
Muhurta Chintamani: cross-check of the Varna and Yoni tables. Checked on: 10-10-2026 - Digital Library of India scan on Internet Archive: B.V. Raman: Muhurtha or Electional Astrology (1948) pp.83-90 kuta chapter
Read for matching only (South Indian Porutham method). Checked on: 10-10-2026 - Internet Archive scan: Brihat Parasara Hora Sastra vol 1 tr. R. Santhanam ch.29-30 (Arudha and Upapada)
Rules for Arudha and Upapada. Checked on: 10-10-2026 - Internet Archive scan: Muhurta Chintamani with Maniprabha, 1.37-39 (Kulika, Kalavela, Yamaghanta, Kantaka, dushta kshana, pp.28-31) and 6.49-51 (nakshatra visha ghati, pp.202-203)
Muhurta Chintamani: Kulika, Kalavela, Yamaghanta, Kantaka and Varjyam. Checked on: 11-10-2026 - Internet Archive scan: MC 6.30 gana verse (p.182, leaf n197): qualitative gana rule only; numeric scores are in the commentary
Muhurta Chintamani: the Gana rule. Checked on: 11-10-2026
Government publications
- India Meteorological Department Positional Astronomy Centre Kolkata: Daily Astronomical Information (Rashtriya Panchang data) 5-12 Oct 2026
Government publication: national Panchang figures, for checking only. Checked on: 10-10-2026
References for matching and checking
- Drik Panchang: Day panchang New Delhi 2026-10-10
Panchang for Delhi on 10-10-2026, for checking only. Checked on: 10-10-2026 - Drik Panchang: Day panchang Mumbai 2026-11-08
Panchang for Mumbai on 08-11-2026, for checking only. Checked on: 10-10-2026 - Drik Panchang: Day panchang Kolkata 2026-03-15
Panchang for Kolkata on 15-03-2026, for checking only. Checked on: 10-10-2026 - Drik Panchang: Day panchang Surat 2026-12-20
Panchang for Surat on 20-12-2026, for checking only. Checked on: 10-10-2026 - VedicMarga: Saturn transit in 2025 (Meena ingress 29 Mar 2025)
Cross-check of Saturn's sign-entry dates (Sade Sati). Checked on: 10-10-2026 - DekhoPanchang: Saturn in Pisces dates
Cross-check of the dates Saturn stays in Meena. Checked on: 10-10-2026 - SmartPuja: Vivah muhurat 2026 list
Marriage muhurat list read; the lists differed from each other, so none was copied. Checked on: 10-10-2026 - The Wedding Focus: Marriage dates list
Marriage date list read; the difference was recorded, not copied. Checked on: 10-10-2026 - DekhoPanchang: Wedding muhurta
Marriage muhurat page read; the difference was recorded, not copied. Checked on: 10-10-2026 - Drik Panchang: Jyeshtha 2026 festival list (Adhika month dates)
Cross-check of Adhik Maas dates, no text taken. Checked on: 10-10-2026
The full method of checking is at Calculation Method, and changes will be announced at Rule Updates.
Calculation Method
How we calculate: Lahiri ayanamsa, whole-sign houses, mean Rahu-Ketu, sources and the date of checking. Also a match of four Panchang examples against Drik Panchang.
Rule UpdatesChanges to the rules and tables behind our tools, with the date they take effect and the tools affected, newest first.