Kairos: lunar timeline, built in Flutter

Kairos is a lunar astronomical timeline, built in Flutter. It renders a dynamically zoomable, scrollable timeline of celestial events on Android and in the browser.

The accuracy comes from Dart ports of Jean Meeus' astronomical algorithms: ELP2000-82 for the Moon and VSOP87 for the Sun, validated against reference data. On top of that it computes moon phases and zodiac transits across four coordinate systems, one tropical and three sidereal.

Keeping it fluid took a custom rendering engine. Instead of the widget tree, the timeline draws on a single canvas: a CustomPaint pipeline with Float32List batch drawing, an SDF-based moon-phase atlas for constant-time phase rendering, a cached TextPainter pool, and binary-search visibility culling. The same engine compiles to a WebAssembly build, so the browser version runs the identical renderer.

Around that it is a finished app: a custom calendar, a bottom sheet with moon-phase and zodiac-transit lists, local notifications with a 90-day lookahead and a configurable lead time, and four color themes (Kairos, Solarized Dark, Tokyo Night, Rosé Pine). It also ships with a Python MCP release server that lets an AI assistant build and deploy it.

Kairos is the first project from sidereal.digital, a small studio for astronomical software, built over 600+ commits since February 2026.

Try it: Kairos demo · Studio: sidereal.digital