1.5 KiB
10. Preserve local-day activity history with its recorded timezone
Status: Accepted; legacy-history migration and repair implemented in issue #99.
Fenris will retain local-day read/write summaries and the boundary evidence needed to interpret them in the existing observation store before three-minute detail expires after 14 days. Each historical summary retains its recorded timezone and day boundaries; this extends ADR 0001 while preserving the UTC hour/day evidence used for endurance projections. Collection derives new measured intervals. Ordered schema migration and explicit repair rebuild legacy summaries from surviving evidence; TUI and CLI readers remain read-only.
UTC hourly summaries alone cannot recover a local day whose midnight falls inside a UTC hour. Preserving labelled local summaries trades arbitrary future timezone reinterpretation for bounded detailed-history retention; retaining all fine-grained intervals indefinitely or estimating a split from UTC summaries would violate the agreed retention or evidence semantics.
Only surviving evidence may be used to derive older local summaries. Dates without enough evidence remain incomplete or unavailable; a measured interval crossing midnight is retained once as shared boundary evidence, never prorated or counted in full on both days. A later timezone change does not silently rewrite historical day boundaries.
The agreed presentation and validation requirements are in the live drive activity specification.