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How the explorer works

We implement NOAA’s fractional-year equations with a conventional 90.833° zenith. TypeScript and Dart implementations are tested against saved US Naval Observatory responses. Allow several minutes of error; terrain, elevation, weather and unusual refraction are not modeled. Daylight duration is identical in both clock scenarios.

Census representative coordinates and IANA time zones are version controlled. Standard offset is the lower January/July offset for these curated US cities. Permanent DST adds one hour only to cities flagged as seasonal. Phoenix and Honolulu retain their exceptions. This illustrates clock differences, not a final bill’s geographic scope.

Supported dates: 2020–2039. Installed IANA rules can change. Refresh data and fixtures before relying on future legal schedules.

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