Legal

Open-source notices

Last updated: September 29, 2026

Your Day, Decoded. is built with open-source software. We are grateful to the authors below. Each package is used under its license, reproduced at the end of this page.

fortuneteller (Saju MCP Server)

https://github.com/hjsh200219/fortuneteller
License: MIT · Copyright (c) Hoshin

Day Master strength, chart structure (格局), balancing element (用神), hidden-stem (支藏干) table, seven special stars (神殺), 10-year Luck Pillars (大運), and the 1900–2200 solar-term table. Adapted and modified; see the notes below.

GeoNames

https://www.geonames.org/
License: CC BY 4.0 · Data © GeoNames (geonames.org), licensed under Creative Commons Attribution 4.0

Birthplace search: city names, coordinates, and time zones (cities with population ≥ 15,000). Filtered and reformatted by us.

lunar-javascript

https://github.com/6tail/lunar-javascript
License: MIT · Copyright (c) 2018 6tail

Four Pillars, annual pillars, Ten God and hidden-stem tables.

Astronomy Engine

https://github.com/cosinekitty/astronomy
License: MIT · Copyright (c) 2019-2023 Don Cross

Planet positions, Ascendant, and transits for Western Astrology notes.

Next.js

https://github.com/vercel/next.js
License: MIT · Copyright (c) 2025 Vercel, Inc.

Web framework.

React

https://github.com/facebook/react
License: MIT · Copyright (c) Meta Platforms, Inc. and affiliates.

User interface library.

Modifications to fortuneteller

Only the calculation modules listed above are used. Four Pillars still come from this site’s own time-zone-aware engine.
Birth moments are passed as absolute instants so births outside Korea are supported.
Charts with an unknown birth time are analyzed without an Hour Pillar.
Caches and Korean text tables were removed; English interpretations are written by us.
If the solar-term table has no entry for a date, no Luck Pillars are shown (upstream defaults to age 5).
Eight further special stars (Heavenly and Monthly Virtue, Literary Star, Academic Hall, Golden Carriage, Goat Blade, White Tiger, Solitary Stars) are calculated by our own code from classical lookup tables; they are not part of fortuneteller.

MIT License

Applies to each software package above, with the copyright line listed for that package. GeoNames data is licensed separately under CC BY 4.0.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

lucide-react icons are used under the ISC License, Copyright (c) Lucide Icons and Contributors.