Calendar boundaries
Known reference dates, leap years, year and month boundaries, solar-term transitions and the civil-date convention are covered by regression tests.
Validation and provenance
Boundaries are tested before they are explained.
A deterministic output is only useful when the edge cases are visible. The release suite tests the boundaries that can change a traditional calendar result.
Time and place
Historical time zones, DST-sensitive locations, location resolution, ambiguous places and unknown birth time paths fail safely or remain explicitly labelled.
Service boundaries
Public pages contain general facts only. RLS, privacy, calculation hashes, encryption and no-personal-data analytics tests protect private results.
Validation evidence is release-specific. A future approved method or dataset version must pass a new regression review rather than silently changing an existing result.