About
Cazimi.
Cazimi is a Mercury retrograde calendar: this website, an iPhone app, a JSON API, and a connector for AI assistants. Every date is computed from the JPL DE421 ephemeris, in UTC to the minute, and published as open data. It is astronomy timing, not a horoscope.
Who makes it
Cazimi is made by Max Rachytskyy, a software developer. The site generator, the iOS app, and the ephemeris script are his work; the app icon is by @ultrasonic66. Write to makrachy@gmail.com about anything here.
Where the dates come from
Stations, cazimi, oppositions, and shadow periods are found by stepping through the JPL DE421 planetary ephemeris with the Skyfield library and locating the minute the apparent geocentric ecliptic speed of a planet changes sign, or its longitude meets the Sun's. The methodology page explains each moment and its precision. The same file of minutes feeds the website, the app, the API, and the assistant connector, so they never disagree.
Open data
- Retrograde ephemeris on GitHub: every Mercury retrograde 1900–2050 and all eight planets 2025–2030, with the script that computes them. CC BY 4.0.
- Zenodo record with a citable DOI for the dataset.
- JSON API: the same answers as the pages, for your own scripts and sites.
- Assistant connector: the retrograde calendar as tools for Claude and other MCP clients.
What Cazimi is not
No natal charts, no horoscopes by sign, no predictions. The site and app state when a planet is retrograde, when it stations, and when the cazimi or opposition falls, and leave the interpretation to you.
Corrections are welcome: if a date looks wrong, email the page link and what you expected.