FA-76023 / Chat ordering and read receipts / Member archive

Insert local day separators into a message list: yesterday direction · case 03

A message stamped slightly in the future by a skewed clock is labelled "Yesterday".

Member previewVariant 3 · 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
today and yesterday	`[[0, "1970-02-20"], [1, "Today"]]`	`[[0, "Yesterday"], [1, "Today"]]`	Failed

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