Moon Phase Calculator implementation

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

t4-125

Effect

Computation or source lookup only

Input and validation requirements

The specification does not define the reference epoch's exact timestamp or the timezone interpretation of date-only inputs. The convention probe produces approximately 48.49% versus 43.19% illumination for the same textual date under two plausible timezone conventions. Very large date intervals also expose precision risk if the implementation subtracts timestamps or reduces phase using insufficient numeric precision.

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": {
    "days_since_reference_new_moon": 0,
    "synodic_month_days": 29.53059
  },
  "expected_outputs": {
    "phase_name": "New Moon",
    "illumination_percent": 0,
    "age_days": 0
  },
  "working": "age = 0 mod 29.53059 = 0 days. theta = 2*pi*(0/29.53059) = 0. cos(theta) = cos(0) = 1. illumination_percent = 100*(1 - 1)/2 = 0%. Age 0 days is New Moon."
}

Other records

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