Panchangam Reference

Sunrise, sunset, moonrise, and moonset ​

panchangam.rise-set

Swiss Ephemeris rise/transit searches produce local sky-marker instants.

Assurance ​

LevelCurrent statement
Documented and traceableYes — the canonical record includes the process and a worked example.
Regression or reproduction checkedLinked to 2 repository test file(s).
Independently source-supportedPartial support only; read the provenance note and limitations before generalizing.

Computation method ​

Method type: algorithm

Convert local civil midnight to UT Julian day and ask Swiss Ephemeris for the next Sun or Moon rise/set event using fixed observer and atmosphere parameters.

Process ​

  1. Localize 00:00 on the requested date in the IANA timezone and convert it to UTC Julian day.
  2. Call swe.rise_trans for Sun or Moon with CALC_RISE or CALC_SET.
  3. Use [longitude, latitude, 0 metres], pressure 1013.25 hPa, temperature 15 C, and Swiss default upper-limb/refraction behavior.
  4. Search sunset from sunrise and next sunrise from the following local midnight.
  5. Convert tret[0] to a whole-second UTC datetime.

Worked example ​

Hyderabad, 2026-06-11 ​

Inputs

  • Location: Hyderabad, Asia/Kolkata
  • Altitude forced to 0 metres
  • Swiss default rise/set flags and atmosphere

Calculation

  1. Search the next solar rise after local midnight, then solar set after that rise.
  2. Search the next lunar rise and set after local midnight.

Result

  • Sunrise: 05:41:11 IST; sunset: 18:50:12 IST
  • Moonrise: 01:55:18 IST; moonset: 14:53:44 IST

Method notes ​

  • Swiss return codes are ignored; polar no-event cases are not represented safely.
  • The Hindu disc-centre/no-refraction convention remains unresolved.

Contract ​

Owning layer: engine-core
Claim kind: deterministic-fact
Time basis: Search from local-midnight Julian day with observer coordinates.

Inputs ​

  • date
  • latitude
  • longitude
  • fixed pressure 1013.25 hPa
  • fixed temperature 15 C
  • hard-coded altitude 0 m

Outputs ​

  • UTC rise/set instants rendered in local timezone

References and evidence ​

Evidence classes: astronomical
Verification states: partially_verified

Swiss Ephemeris documents the current astronomical-default behavior; issue 177 tracks the Hindu-calendar convention decision and multi-city comparisons.

panchangam.rise_set_convention ​

Evidence class: astronomical
Verification state: partially_verified
Locator: Swiss Ephemeris Programmer's Documentation sections 8.12 and 8.12.1; convention decision and comparison gap tracked in GitHub issue 177
Last reviewed: 2026-08-27
Scope: Precisely traces the current astronomical-default rise_trans behavior: upper limb with refraction, fixed 1013.25 hPa and 15 C, and zero-metre altitude passed by all engines. It does not establish that this is the intended Hindu-calendar convention or independently verify multiple city/date cells.

Sources ​

  • Swiss Ephemeris — Astrodienst; Swiss Ephemeris 2.10 Programmer's Documentation and pyswisseph runtime used by the repository; authority type: astronomical_reference

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

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 ​

  • All engines use the astronomical upper-limb/refraction default, ignore Location.alt and return codes, and lack a registered multi-city decision fixture for the intended public convention.

Implementation ​

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