Panchangam Reference

Nakshatra and Pada ​

panchangam.nakshatra

Sidereal lunar longitude selects one of 27 Nakshatras and one of four Padas.

Assurance ​

LevelCurrent statement
Documented and traceableYes — the canonical record includes the process and a worked example.
Regression or reproduction checkedLinked to 4 repository test file(s).
Independently source-supportedNot independently verified at this level; current behavior is regression-pinned.

Computation method ​

Method type: formula

Divide sidereal lunar longitude into 27 equal Nakshatras and each Nakshatra into four Padas, then solve the enclosing longitude crossings around sunrise.

Process ​

  1. Set Nakshatra size N=360/27 degrees.
  2. At sunrise choose n=floor(M/N) modulo 27.
  3. Bisect the Moon model at n*N in [sunrise-2 days, sunrise] and at (n+1)*N in [sunrise, sunrise+2 days].
  4. Compute Pada as floor((M/N)*4) modulo 4 plus 1.
  5. Map n through NAKSHATRA_NAMES and expose whole-second UTC boundaries.

Formulae ​

Nakshatra and Pada ​

text
N = 360 / 27
n = floor(M / N) mod 27
pada = floor((M / N) * 4) mod 4 + 1
  • M: selected engine Moon longitude
  • n: Nakshatra index
  • pada: 1 through 4

Worked example ​

Hyderabad sunrise, 2026-06-11, Drik Ganita ​

Inputs

  • Moon longitude: 358.4708221648 degrees
  • N = 13.3333333333 degrees

Calculation

  1. floor(358.4708221648/N) modulo 27 = 26, Revati.
  2. The Pada formula yields 4.
  3. Bisect the Drik Moon at the two Revati boundaries.

Result

  • Revati, Pada 4
  • Span: 2026-06-10 09:21:40 to 2026-06-11 08:16:35 IST

Method notes ​

  • Surya Siddhanta and Vakya use their own Moon functions, so their boundaries can differ from Drik.

Contract ​

Owning layer: engine-core
Claim kind: deterministic-fact
Time basis: Active at local sunrise with UTC boundary crossings.

Inputs ​

  • engine lunar longitude

Outputs ​

  • Nakshatra name
  • start/end
  • Pada

References and evidence ​

Evidence classes: astronomical, textual
Verification states: partially_verified, engine_pinned

Drik has representative comparisons; non-Drik spans are engine-pinned.

drik.sidereal_positions ​

Evidence class: astronomical
Verification state: partially_verified
Locator: Swiss Ephemeris Programmer's Documentation sections 3, 5.8 and 12.2 for calc_ut, sidereal flags and ayanamsa modes; representative date checks in tests/test_drik_engine.py and tests/test_ayanamsa.py
Last reviewed: 2026-08-27
Scope: Traces the Drik longitude API and preserves representative outputs. The current register does not contain an exhaustive independently published position-and-transition fixture, and it establishes no interpretive doctrine.

Sources ​

  • Swiss Ephemeris — Astrodienst; Swiss Ephemeris 2.10 Programmer's Documentation and pyswisseph runtime used by the repository; authority type: astronomical_reference
  • Drik Panchang day and festival pages — Drik Panchang; Location- and date-specific web pages; authority type: published_panchangam

panchangam.non_drik_engine_outputs ​

Evidence class: astronomical
Verification state: engine_pinned
Locator: tests/test_surya_siddhanta_engine.py and tests/test_vakya_engine.py

Scope: Regression tests preserve the current Surya Siddhanta and Vakya Pancha-Anga and sky-event outputs. No independent published-Panchangam comparison set is registered, so engine-pinned output must not be described as externally verified.

Sources ​

  • No external source is registered for this claim.

panchangam.calendar_semantics ​

Evidence class: textual
Verification state: needs_locator
Locator: No precise locator is registered.

Scope: Samvatsara, Ayana, Ritu, lunar-month, Paksha, weekday and Rasi labels combine astronomical calculations with calendar rollover conventions. They require criterion-level locators and regional-scope notes; astronomical correctness alone does not verify the naming convention.

Sources ​

  • Muhurtha (Electional Astrology) — B. V. Raman; UBS Publishers' Distributors, 1993, ISBN 9788185674681, 181 catalogued pages; authority type: modern_synthesis

The complete machine-readable source registry is available in provenance.json. A regression fixture or same-code reproduction is not independent verification.

Reproduce and review ​

Run the linked tests, then the complete offline contract:

bash
python tools/verify_project.py

Public surfaces ​

  • python-library
  • mcp
  • ics
  • website

Limitations ​

  • Names and boundaries inherit engine and ayanamsa choices.

Implementation ​

This route is generated from computations.json. Edit the registry and canonical reference prose in the same pull request as a behavior change.