PART I - THE CALENDAR ACCIDENT
The Operating Problem of a Multi-World Civilisation

Before designing a calendar for the Solar System, it is worth being clear about the problem we are trying to solve.

Humanity has never needed a civil-time architecture for more than one inhabited world. Every calendar in history has developed within the same basic astronomical environment, while every organisation, government and society has ultimately shared one planetary day and one planetary orbit.

That constraint may not last forever.

If human civilisation spreads across planets, moons, asteroids and artificial habitats, communities will encounter radically different physical cycles while still needing to work, trade, travel, record history and coordinate with one another.

Part I approaches that problem through three steps:

CIVILISATION — what changes when the Solar System stops being a collection of destinations and starts becoming human geography?

INHERITANCE — which parts of the calendar we already use are physical necessities, and which are convenient accidents of living on Earth?

REQUIREMENTS — once those assumptions are exposed, what actually needs to be shared across many worlds?

The movement matters.

Before deciding what a Solar-System calendar should look like, we first need to understand why one might be needed, what Earth has been quietly doing for us, and which functions are important enough to preserve when that convenient astronomical background disappears.

Only then can we design.