Sources
Sources and Calculation Notes
Indian Panchang references, astronomical sources, and comparison data used to calculate and check Samvat dates.
Last reviewed
How Sources Are Used
Samvat calculates its calendar results directly. Published astronomical and Panchang references are used to define conventions, document festival rules, and check sampled results.
When comparing two calendars, match the city, timezone, lunar month system, and observance moment. Different assumptions can produce different civil dates without either tradition being incorrect.
Primary and Scholarly References
These sources cover Indian Panchang conventions, planetary and lunar models, time conversion, and independent comparison data.
- Indian Astronomical EphemerisPositional Astronomy Centre, India Meteorological Department.
- Rashtriya PanchangIndian reference for Panchang elements and principal festivals.
- VSOP87 planetary theoryBretagnon and Francou planetary theory.
- ELP2000 lunar theoryChapront-Touze and Chapront lunar theory.
- Julian Date definitionUS Naval Observatory Astronomical Applications Department.
- NASA/JPL HorizonsIndependent sampled astronomical position comparisons.
- Swiss EphemerisIndependent sampled Lahiri and lunar-phase comparisons; not used for live calculations.
Festival and Cultural Rules
Festival definitions use explicit rules such as Shravana Shukla Purnima for Raksha Bandhan and Kartik Krishna Amavasya during Pradosha for Diwali.
Regional practice can select another checkpoint or civil date. Samvat records variants as named rules rather than silently replacing a calculated date.
Classical Jyotisha Rules
Chart positions are astronomical outputs, while Drishti, Dasha, Gochara, and yoga formations add declared traditional rules. Samvat keeps the calculation evidence and cited rule separate from outcome interpretation.
- Brihat Parashara Hora ShastraVimshottari Dasha framework and Parashari Graha Drishti source used by the calculation modules.
- Phaladeepika, chapter 6Source-bound Pancha Mahapurusha and Kesari Yoga formation rules.
- Phaladeepika, chapter 26Classical Gochara reference from the natal Moon.
Reporting a Difference
A useful correction includes the Samvat URL, city, timezone, expected value, comparison source, and the exact rule or timestamp being compared.
That evidence allows a calculation defect, convention difference, or regional variant to be identified separately.