How exactly a date is pinned — exact, estimate, or announced.
Precision describes the date, not our knowledge of it. Exact means the date is fixed and known. Estimate means it is derived astronomically or arithmetically and is subject to local confirmation — most Islamic dates, which depend on a sighting. Announced means it was set by decree for that year only and no rule predicts it.
It is a separate axis from assurance and the two are genuinely independent. A ministry may announce a date by decree — announced precision, and verified assurance, because we read the decree. A far-future Eid computed from a rule is an estimate however well sourced the rule is.
Systems that branch on dates should branch on this field. Printing an estimate as a hard date is the error it exists to prevent.
Precision is about the date; the evidence tier is about what the date rests on. A Tier 1 date can still be an estimate — the rule is certain, the day it lands on is not.
See also evidence tier · assurance · observance · edition
We hold this as precision on every computed date. See what we hold.