Fixed points · The immovable · Element
The list
What genuinely cannot move.
The part
What it is
With the authority that fixes it: a statute, a contract, a regulator, an external event.
Where no authority can be named, the date is probably not fixed.
The smallest level
The attributes it carries
Each attribute is one of the framework’s shared types. What a date is, and how it is written, is defined once for the whole model — the note here says what it means in this particular place.