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

instrument mechanism / verified-clean

# Time Zone / Local Solar Time Offset mechanism

The inspectable method record for Time Zone / Local Solar Time Offset, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

Core arithmetic matches the standard solar-time correction under the stated unit and sign assumptions, but the instrument should not ship as specified. Add clock_time and an explicit timezone-meridian/DST policy, define the equation-of-time approximation and sign convention, and label the result as approximate true local solar time rather than an exact civil-time conversion.

- The formula is standard only when longitude is positive east, timezone_meridian is the local standard-time meridian in degrees east, and equation_of_time is defined as apparent solar time minus mean solar time. Under those conventions it computes true solar time minus clock time, but the specification does not state the sign convention for 'difference' or 'offset from clock time'.

- The input 'timezone' is underspecified: the formula requires a numeric timezone meridian, while a timezone may instead be a UTC offset, named time zone, or daylight-saving-adjusted civil time.

- The declared inputs omit clock time, which is required to compute the stated 'local solar time' output; the formula computes only an offset.

- The equation-of-time approximation formula is not provided, so date-dependent results cannot be reproduced or verified from this specification alone.

## Units and conventions

- Longitude is measured in decimal degrees, positive east and negative west, within -180° to +180°.

- timezone_meridian is measured in decimal degrees east; for a fixed UTC offset without DST it is 15° multiplied by the UTC offset in hours.

- The factor 4 min/degree is based on Earth's nominal 24-hour rotation: 360°/24 h = 15°/h.

- equation_of_time is in minutes and uses the convention apparent solar time minus mean solar time.

- Clock time is civil local clock time in minutes or HH:MM, with any daylight-saving adjustment already resolved.

- The test vectors use supplied equation-of-time values from an assumed approximation; the specification must identify the exact approximation and date/time convention.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "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."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

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.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/time-zone-local-solar-time-offset/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/time-zone-local-solar-time-offset/implementation/>)[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`

- `BOUNDARY_HAZARD_CATALOG.json`