Panchangam Reference

Daily Sankramana assignment ​

panchangam.sankramana-day

Exact solar ingress is assigned to a Panchangam day with the project's after-sunset convention.

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-supportedNot recorded as independently verified. The disclosed provenance state remains authoritative.

Computation method ​

Method type: algorithm

Detect a solar-sign change across today's daylight or after yesterday's sunset, bisect the exact 30-degree crossing with the selected engine Sun, and assign after-sunset ingress to the following Panchangam day.

Process ​

  1. Compare Sun-sign indices at today's sunrise and sunset.
  2. If they differ, bisect the engine Sun between sunrise and sunset at the entered sign's boundary.
  3. Otherwise compare yesterday's sunrise and sunset with today's sunrise.
  4. When the sign changed after yesterday's sunset, bisect in [yesterday sunset, today sunrise] and assign it to today.
  5. Return no event when neither condition holds.

Worked example ​

Hyderabad, 2026-06-15, Drik Ganita ​

Inputs

  • Sunrise: 05:41:40 IST
  • Sunset: 18:51:22 IST
  • Sun changes from Vrishabha to Mithuna during daylight

Calculation

  1. Sunrise and sunset sign indices differ.
  2. Bisect Drik Sun longitude at 60 degrees between sunrise and sunset.

Result

  • Entered Rashi: Mithuna
  • Ingress JD: 2461206.8076462564; local time 12:53:00 IST; assigned to 2026-06-15

Method notes ​

  • Day assignment is a convention separate from the astronomical crossing instant.

Contract ​

Owning layer: engine-core
Claim kind: regional-convention
Time basis: Ingress after local sunset is assigned to the next Panchangam day.

Inputs ​

  • sunrise
  • sunset
  • solar longitude crossing

Outputs ​

  • entered Rashi
  • ingress Julian day
  • Sankranti flag

References and evidence ​

Evidence classes: astronomical, regional_convention
Verification states: needs_locator

Crossing code is tested; day-assignment semantics need exact locator evidence.

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 ​

  • Day assignment is conventional and distinct from the astronomical crossing instant.

Implementation ​

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