The standard behind the label — what a row has to have before it can claim a tier.
Assurance is the method, not the mark. It is the standard that decides what a row is allowed to claim, and the thing a customer reads — the evidence tier — is what the standard produced.
The standard has three requirements and they are not negotiable. A row reaches the top only if somebody opened the instrument itself: a gazette, a statute, a central bank notice, a ministerial decree, and read the date there. Two sources count as agreement only if they are genuinely independent — a compilation and a second compilation drawing on the first are one source wearing two hats. And no grade rises without a new retrieval; a pre-commit check enforces it, because the alternative is a grade that drifts upward as people get more comfortable with a record.
Until September 2026 the standard and the label were the same three words, and that was the mistake. Naming the OUTCOME invited a claim about the world, and 111 rows reached 'verified' through a script that matched an observance name against a document and never compared the date. The tiers name the ACT instead: a row cannot become Authority-sourced by accident, because the label says what was done to earn it.
The retired words were verified, corroborated and compiled. They went for two reasons: they signalled a confidence we had not measured, and they could not tell an official document from a calendar reference — a distinction the four tiers make and three words could not. The standard did not change; it stopped doubling as a badge.
Assurance is about our sourcing — how well we know it. Precision is about the date itself — how exactly it is fixed. A date can be poorly evidenced and exact, or well evidenced and approximate.
See also evidence tier · precision · verified · corroborated · compiled
Filter to what an authority actually said with min_assurance=verified — the parameter keeps its name and its meaning. See what we hold.