Source: https://guthlabs.ai/docs/instruments/time-zone-local-solar-time-offset/implementation/

instrument implementation / implementation-contract

# Time Zone / Local Solar Time Offset implementation

A source-bound implementation contract for Time Zone / Local Solar Time Offset; 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**: t5-118

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification omits longitude-range validation and antimeridian normalization. An extreme longitude produces Infinity in JavaScript arithmetic, and interpreting longitude signs differently can change the result by 600 minutes. The formula also has no explicitly defined wrap branch at the ±180-degree boundary.

## 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": {
    "longitude_deg_east": -74.006,
    "timezone_utc_offset_hours": -5,
    "timezone_meridian_deg": -75,
    "date": "2024-01-15",
    "clock_time": "12:00",
    "equation_of_time_min": -9
  },
  "expected_outputs": {
    "offset_from_clock_min": -5.024,
    "local_solar_time": "11:54:58.56"
  },
  "working": "Longitude term = 4 × (-74.006 - (-75)) = 4 × 0.994 = 3.976 min. Offset = 3.976 + (-9.000) = -5.024 min. Local solar time = 12:00:00 - 5.024 min = 11:54:58.56."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/time-zone-local-solar-time-offset/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/time-zone-local-solar-time-offset/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/time-zone-local-solar-time-offset/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-tranche5/tranche5-results.json`