[luannn010]

Summary

• Derive per-habit streak scalars from validated Journal civil dates, without storing streaks or retaining private source objects.
• Honor selected history, creation/archive boundaries and gaps; use UTC date arithmetic across leap/year/DST boundaries.
• This preparatory helper is wired into the dependent Journal feedback slice. It adds no visible feature by itself.

Testing

• 20 focused tests passed, including 100,000 completion records and 100 habits.
• Independent lead review accepted the exact helper and tests.
• Hosted checks qualify this exact commit. Risk: derived view data; no schema, key or persistence change. Undo: revert this slice before its consumer.

Co-authors

none

AI usage

• Written by hand, with no AI
• Harness and version: Codex desktop, codex-cli 0.160.0.
• Models: gpt-6.1-sol (implementation, tests, design contract and independent review); gpt-6-luna (read-only design freshness inventory).
• Effort: medium.
• Human role: requested the design-gap audit, implementation and focused update PRs; merge review remains pending.
• Sources: project-owned approved design revision 7a231593a82ce97780b1bb9ef2526330adbd7e57, Notes frames journal-today/journal-history/phones-more and Motion habit. Historical-date carry with an honest through-date is an explicitly documented beta clarification. No external implementation copied; existing notices retained.

Checklist

• Works on Windows, macOS and Linux
• Complete beta/design/native performance qualification
• No credentials, profiles, private design exports or build outputs included