Source: https://guthlabs.ai/docs/instruments/synodic-period-calculator/implementation/

instrument implementation / implementation-contract

# Synodic Period Calculator implementation

A source-bound implementation contract for Synodic Period Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-209

**Effect**: Computation or source lookup only

## Input and validation requirements

The raw arithmetic formula has exploitable failure points at zero periods and equal periods, producing undefined or infinite results. A signed-period interpretation also changes whether an input is valid and can produce a different semantic result unless the convention is explicitly enforced.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "body_1": "Earth",
    "T1": 365.256,
    "T1_unit": "days",
    "body_2": "Mars",
    "T2": 686.98,
    "T2_unit": "days"
  },
  "expected_outputs": {
    "synodic_period": 779.934235,
    "unit": "days"
  },
  "working": "S = T1*T2/|T2-T1| = (365.256*686.98)/|686.98-365.256| = 250923.56688/321.724 = 779.934235 days."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/synodic-period-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/synodic-period-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/synodic-period-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`