Open Biorhythms — dr. Jerzy Sikora's method, verified and free

The open, verified engine and specification of dr. Jerzy Sikora's biorhythm method — powering the free app at aimy.bio.

Try it — no install: npx aimy-bio-open-biorhythms 1990-05-15

What this is

This repository is the reference engine (src/engine.js) and the canonical specification (docs/method.md) of dr. Jerzy Sikora's discrete-phase biorhythm method — a tribute to his work, not a product. The method is dr Jerzy A. Sikora's — a Polish researcher (b. 1930, Cieszyn), the father of Polish biorhythmics. It is privacy-first and free: there is no telemetry here, no account, and no dependency to install — just math you can read line by line and verify yourself.

Reconstructed from dr. Sikora's own book, Biodiagram prawdę Ci powie (KAW, 1983), and validated digit by digit against his own worked examples — e.g. the poet Mickiewicz's biorhythm (F22/P15/I1) and the Goethe+Schiller biopowinowactwo (compatibility) match (F100/P86/I82) — then pinned by 741 + 211 golden vectors so it can't drift.

See it live

Live app → https://aimy.bio — free, 8 languages, works offline, nothing to install.

Verify it yourself

No trust required — clone it and run the same golden-vector suite that CI runs on every commit:

git clone https://github.com/fiedoruk/aimy-bio-open-biorhythms
cd aimy-bio-open-biorhythms
npm test   # 741 Sikora + 211 BioMatch golden vectors -> ALL GREEN

Zero dependencies — plain Node.js, nothing to install first.

Or try it on your own birthday: node examples/today.mjs 1990-05-15

Install / use as a package

No cloning required — try it directly with npx:

npx aimy-bio-open-biorhythms 1990-05-15   # or, once installed: aimy-biorhythm 1990-05-15

Add --json for machine-readable output, or --help for all CLI options (--date).

Or add it as a dependency and use the engine directly:

npm i aimy-bio-open-biorhythms

import { getBiorhythmsFor } from 'aimy-bio-open-biorhythms';
console.log(getBiorhythmsFor(new Date(1990, 4, 15), new Date()));

Use with AI assistants (MCP)

The package also ships a zero-dependency MCP server (aimy-bio-mcp), so AI assistants can actually compute dr. Sikora's method instead of hallucinating generic sine waves. Zero PII by design: dates are processed in flight — nothing is stored, logged, or sent anywhere.

Claude Code — one command:

claude mcp add biorhythms -- npx -y --package=aimy-bio-open-biorhythms@latest aimy-bio-mcp

Claude Desktop (or any MCP client) — claude_desktop_config.json:

{
  "mcpServers": {
    "biorhythms": {
      "command": "npx",
      "args": ["-y", "--package=aimy-bio-open-biorhythms@latest", "aimy-bio-mcp"]
    }
  }
}

(Note the --package= form — plain npx aimy-bio-open-biorhythms runs the default CLI bin, not the MCP server.)

Tools: biorhythm_for_date (full state for any date) · critical_days (upcoming critical transitions and strong-phase starts) · biomatch (two-person compatibility, biopowinowactwo).

The method in 30 seconds

Every day, in every cycle, is classified into exactly one of four states:

| Symbol | Name | Meaning | |---|---|---| | + | High | Active phase | | − | Low | Passive phase | | X | Critical day | Transition from high to low | | 0 | Zero day | Regeneration — transition from low to high |

That symbol — not a percentage, not a curve — is the ground truth of the method.

This is unmodified output of src/engine.js (born 1990-05-15, on 2026-07-01) — reproduce it yourself with npm test.

{
  "daysAlive": 13197,
  "physical": {
    "symbol": "-",
    "day": 18,
    "length": 23,
    "percent": 9
  },
  "emotional": {
    "symbol": "+",
    "day": 9,
    "length": 28,
    "percent": 82
  },
  "intellectual": {
    "symbol": "-",
    "day": 30,
    "length": 33,
    "percent": 30
  }
}

Full specification → docs/method.md

What's inside

• docs/method.md — the full, verifiable method specification (day-count, phase tables, BioMatch).
• docs/philosophy.md — why this exists and why it's open.
• Polish / po polsku: docs/pl/method.md · docs/pl/philosophy.md
• src/engine.js — the reference implementation, zero dependencies.
• data/README.md — data dictionary for the 741 + 211 golden vectors that pin correctness.

Cite this repository

This repository ships a CITATION.cff, so GitHub exposes a "Cite this repository" button on the repo page. If you use this method or engine, please cite it and link back to https://aimy.bio.

Licensing

• src/** — MIT.
• docs/** and data/** — CC BY 4.0 (attribution to aimy.bio required).

Using this? Link back

Docs & data are CC BY 4.0 — reuse freely, just keep the credit. Paste-ready:

Biorhythm engine & method spec: aimy.bio — https://aimy.bio (CC BY 4.0)

Or drop this badge in your README:

[![biorhythm engine: aimy.bio](https://img.shields.io/badge/biorhythm_engine-aimy.bio-2ea44f)](https://aimy.bio)

Contributing

PRs for docs, translations, and UX ideas are welcome under the DCO. The engine math is a mirror of the canonical source that powers aimy.bio — PRs changing the math in src/engine.js will be redirected there instead of merged here. See CONTRIBUTING.md.

A tribute to the work of dr. Jerzy Sikora.