Calcgrid

Open deterministic calculation and evidence-data engine for AI agents and people: finance, loans, health, fitness, math, statistics, unit conversion, pinned IANA time-zone rules, science and engineering, plus source-traceable mainland China working days and official UK bank holidays, lunar calendar and solar terms; available as HTML, Markdown, JSON API, MCP and A2A. The public Agent Card highlights 24 priority calculators, including a worldwide CLDR weekday baseline, broad OpenWorkdays national-scope reference, source-traceable mainland China and UK working-day tools and pinned IANA local-time resolution and transition tools, plus search and a generic execution entry; the A2A endpoint accepts every calculator id. Read-only, deterministic calculations; every result carries the formula, sources and an ISO 8601 timestamp.