KDS Calendar: Normative Specification, Conformance Framing, and Comparative Evaluation of an Equinox-Anchored Civil Calendar

KDS Calendar is a solar civil calendar proposal anchored to the March equinox that jointly preserves four properties rarely found together in calendar reform: astronomical annual anchoring, uninterrupted seven-day week continuity, regular 30-30-31 quarter structure, and full interoperability with SI/UTC operational timekeeping. The canonical year begins at 00:00 UTC on the civil UTC day that contains the March equinox instant. Extended years (366 UTC days between consecutive starts) receive one extra day at the end of M12 without breaking the week. The architecture strictly separates CANON (globally uniform date identity) from PROJECTION (time zones, DST, seasonal names, local display). Included files • KDS_Calendar.pdf — full normative specification, pseudocode, comparative evaluation and year-start table 2025–2035 • kds-converter.html — standalone, offline Gregorian-to-KDS date converter (no external dependencies, works directly in any browser) Scope and demonstrator note This record is a specification-oriented concept paper and reference implementation package. The HTML demonstrator implements the exact mapping algorithm from §6 of the paper and uses a fixed equinox table compiled from the U.S. Naval Observatory Earth's Seasons dataset (retrieved 17 March 2026, normalized to UTC). It is provided for demonstration, education and prototyping purposes only and should not be treated as the final conformance authority for production implementations. For full normative rules, conformance requirements and comparative analysis please consult the PDF manuscript.