FA-18699 / Time representation / Member archive

Noon coordinate day extraction ignores half-day shift or double-carries exact midnight · case 04

The decoded time state disagrees with the explicit regression oracle for day.

Member previewVariant 4 · 3 implementations · 12 checks per implementation

Case contract

Controlled astronomical coordinate counts exact rational days from a noon origin. A civil day index uses midnight; coordinate J corresponds to civil index floor(J+1/2) and fraction J+1/2-index. One civil day has 86400 exact ticks. Return civil index, rational tick within day, noon-relative displacement, modified coordinate J-2400000.5, exact roundtrip and before-noon flag. No historical calendar conversion is modeled.

Why this case matters

Clock transfer and timestamp consumers require preserved coordinate, phase, validity and elapsed-time semantics.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
fixture 3	`[0, "86400", "43200", "-2400000", "1/2", false, "1", "43200"]`	`[1, "0", "-43200", "-2400000", "1/2", true, "1", "43200"]`	Failed

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