FA-18718 / Time representation / Member archive

Modified day coordinate omits half-day epoch adjustment · case 03

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

Member previewVariant 3 · 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 1	`[0, "43200", "0", "-2400000", "0", false, "1", "86400"]`	`[0, "43200", "0", "-4800001/2", "0", false, "1", "86400"]`	Failed

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