Date

What this is

A date is a point in calendar time. In this system dates are always represented as ISO 8601 strings (YYYY-MM-DD). A date is not a timestamp — it carries day-level precision, not sub-second. It is not a history in the mathematical sense (history) — it is a human-readable label for when something happened, not an element of the history monoid T. A Date MUST be a valid ISO 8601 date string in YYYY-MM-DD format. It MUST be in UTC — no timezone offsets.

Open questions

• Whether a full datetime (YYYY-MM-DDTHH:MM:SSZ) should be an alternative or replacement for cases where day-level precision is insufficient.