Samvatsara name

panchangam.samvatsara

Elapsed Kali-era solar years and the current lunar month map to the 60-year Telugu cycle.

Assurance

Level	Current statement
Documented and traceable	Yes — the canonical record includes the process and a worked example.
Regression or reproduction checked	Linked to 1 repository test file(s).
Independently source-supported	Not recorded as independently verified. The disclosed provenance state remains authoritative.

Computation method

Method type: formula

Count mean sidereal years since the code Kali epoch, shift by lunar-month number so the name changes at Chaitra, then apply the repository's 60-name anchor.

Process

1. Remove Adhika or Nija and convert Chaitra..Phalguna to month number 1..12.
2. Set ahargana=JD-588465.5.
3. Compute elapsed=floor((ahargana+(4-month_number)*30)/365.25636).
4. Return SAMVATSARA_NAMES[(elapsed+12) modulo 60].

Formulae

Sixty-year index

A = JD - 588465.5
y = floor((A + (4 - month_number) * 30) / 365.25636)
index = (y + 12) mod 60

• month_number: Chaitra=1 through Phalguna=12
• y: elapsed project sidereal years
• 12: project cycle anchor

Worked example

Hyderabad sunrise, 2026-06-11

Inputs

• JD: 2461202.5077662035
• Maasam: Adhika Jyeshtha, base month number 3

Calculation

1. A=1,872,737.0077662035 days.
2. floor((A+30)/365.25636)=5,127.
3. (5,127+12) modulo 60=39.

Result

• SAMVATSARA_NAMES[39]: Parabhava

Method notes

• The anchor and month shift are project conventions whose criterion-level locator remains unresolved.

Contract

Owning layer: engine-core
Claim kind: regional-convention
Time basis: Year flips at Chaitra under the southern Chaitradi convention.

Inputs

• Julian day
• Maasam

Outputs

• 60-year-cycle name

References and evidence

Evidence classes: textual, regional_convention
Verification states: needs_locator

Expected years are regression-tested; epoch/offset semantics need exact source documentation.

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

• tests/test_samvatsara.py

Run the linked tests, then the complete offline contract:

python tools/verify_project.py

Public surfaces

• python-library
• mcp
• ics
• website

Limitations

• Cycle anchoring follows the documented Telugu Chaitradi convention.

Implementation

• owner: telugu_panchangam/engines/base.py — samvatsara_name
• owner: telugu_panchangam/engines/drik.py — DrikGanitaEngine._samvatsara
• owner: telugu_panchangam/engines/surya_siddhanta.py — SuryaSiddhantaEngine._samvatsara

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