FA-76015 / Chat ordering and read receipts / Member archive

Insert local day separators into a message list: today in local zone · case 05

Shortly after local midnight the current day is labelled "Yesterday" because "today" is computed in UTC.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

stamps are ascending unix seconds; offset_min is the viewer's UTC offset in minutes. A separator [index, label] precedes the first message of each local calendar day: "Today" for the local day containing now, "Yesterday" for the one before, otherwise the ISO local date.

Why this case matters

Day headers anchor chat history in time; zone mistakes split or merge days around midnight.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
east of UTC after local midnight	`[[0, "1970-03-04"]]`	`[[0, "Today"]]`	Failed

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