# Tasks: datetime-spec-conformance

## 1. Source refactors (additive only)

- [x] 1.1 Add `expandRecurrenceSize`, `businessDaysBetweenDuration`, `businessDaysBetweenSize` histograms in `src/otel/datetime-otel.ts`.
- [x] 1.2 Extend `recordExpandRecurrence(durationMs, size?)` and `recordBusinessDaysBetween(count, durationMs?)` additively.
- [x] 1.3 Wire size + duration recording in `src/recurrence/recurrence.ts::expandRecurrence` and `src/business-days/business-days.ts::businessDaysBetween`.
- [x] 1.4 Re-export the new histograms from `src/index.ts`.
- [x] 1.5 Update `src/otel/datetime-otel.md` to document the new instruments.

## 2. Spec annotations

- [x] 2.1 Add a `**Verified by:**` line under every requirement in `openspec/specs/datetime/spec.md`.
- [x] 2.2 Clear the retroactive-ticking marker phrase in `openspec/archive/2026-04-19-enterprise-datetime/tasks.md`.

## 3. Pinning tests

- [x] 3.1 Add `src/datetime.spec-conformance.test.ts` covering DT-01..DT-10 (20 tests).

## 4. Verify

- [x] 4.1 `bunx turbo lint typecheck test --filter=@suaveplan/datetime` green.
- [x] 4.2 `bunx turbo test:coverage --filter=@suaveplan/datetime` 100/100/100/100.
- [x] 4.3 `bun scripts/openspec-conformance.ts @suaveplan/datetime` exits 0.