When HKT calendars and UTC warehouses disagree
Day-one latency cohorts can shift when midnight moves—not when the network does.
Application teams serving Hong Kong often mix UTC event stores with HKT product calendars. A cohort day that spans the wrong midnight rewrites every diagnostic cell without a single feature ship.
Collector upgrades that change trace stitching create similar ghosts. Returning sessions look new; p95 numbers swing for pipeline reasons.
Before celebrating a lift, list SDK versions, correlation rules, and timezone settings beside the chart. Our Cross-Hop Correlation Review always opens with that checklist.