Panchangam Reference

Ekadashi, Amavasya, Pournami, and Pradosham flags ​

panchangam.special-lunar-days

Sunrise and deciding-moment Tithi rules assign recurring lunar observances and Ekadashi names.

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: decision-table

Classify recurring lunar days from sunrise and sunset Tithi indices, combine Pradosham with weekday, detect Sankranti from solar-sign changes, and name Ekadashi from Maasam/Paksham overrides.

Process ​

  1. At sunrise set Ekadashi for indices 10 or 25, Pournami for 14, and Amavasya for 29.
  2. Set Pradosham when index 12 or 27 is active at sunrise or sunset; add Shani/Soma for Saturday/Monday.
  3. Detect a solar-sign change across the engine's comparison window for Sankranti.
  4. For Adhika Maasam name Shukla/Krishna Ekadashi Padmini/Parama.
  5. Otherwise use the base Maasam/Paksham lookup and append Vaikunta for Shukla Ekadashi with Sun in Dhanu.

Worked example ​

Hyderabad, 2026-06-11, Drik Ganita ​

Inputs

  • Sunrise Tithi index: 25
  • Maasam/Paksham: Adhika Jyeshtha/Krishna
  • Weekday: Thursday
  • No solar-sign change

Calculation

  1. Index 25 matches Krishna Ekadashi.
  2. The Adhika-Krishna override selects Parama.
  3. Other special indices and weekday combinations do not match.

Result

  • is_ekadashi=true; name=Parama Ekadashi
  • Other lunar-day and Sankranti flags are false

Method notes ​

  • Deciding moments and names follow maintained Telugu conventions rather than a universal calendar rule.

Contract ​

Owning layer: engine-core
Claim kind: regional-convention
Time basis: Panchangam-day deciding moments; names use Telugu Amanta convention.

Inputs ​

  • Maasam
  • Paksham
  • Tithi at deciding moments
  • weekday
  • solar sign

Outputs ​

  • observance flags
  • Ekadashi name

References and evidence ​

Evidence classes: published_panchangam, regional_convention
Verification states: partially_verified, engine_pinned

Drik has representative comparisons; non-Drik flags are regression-pinned.

festivals.forward_year_2027_2028 ​

Evidence class: published_panchangam
Verification state: partially_verified
Locator: 1 DP_VERIFIED cell; 29 ENGINE_PINNED cells in the fixture

Scope: Only cells marked DP_VERIFIED are independently verified.

Sources ​

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.

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
  • generated-data

Limitations ​

  • Naming and deciding moments follow documented Telugu conventions.

Implementation ​

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