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Evidencespacetime-417

Unexpected behaviour from at least isEqual() when using UNIX epoch date (1970-01-01)

spacetime#417, at commit 0464eca. A closed issue from a repository Credda did not choose.

LIVE2026-09-20

RIGHT_FAILURE

executed against the upstream checkout.

Outcome
PATCH_REJECTED
Wall time
152.0s
Checks
5 passed of 5 applicable

RECORDED

NOT_GRADED

graded from the transcript committed with this case.

Outcome
not recorded
Checks
none run
Repository
spencermountain/spacetime
Issue
#417
Pinned commit
0464ecaebb935bc89fe2507fc4e0b478362c4a57

01The signal

The report, exactly as it was filed.

Nothing paraphrased or cleaned up. The mess is the thing under test.

spacetime#417 · as filedcommit 0464eca

Unexpected behaviour from at least isEqual() when using UNIX epoch date (1970-01-01)

```js
> spacetime('1970-01-01').isEqual('1970-01-01')
null
> spacetime('1970-01-02').isEqual('1970-01-02')
true
> spacetime('1970-01-02').isEqual('1970-01-01')
null
> spacetime('1970-01-01').isEqual('1970-01-02')
false
```

Should only return null when passed an invalid date?
Issue
#417
Commit
0464ecaebb935bc89fe2507fc4e0b478362c4a57
Why this commit
The first parent of the fix commit 656edbb32c512a939fea2f644f3a610ed70f348e, which GitHub binds to this issue via CROSS_REFERENCED_PR. Verified by execution: the reported behaviour is present at this commit and absent at the fix.
How the text was obtained
Fetched verbatim via the GitHub GraphQL API. Title on the first line, body unmodified below it. Nothing was paraphrased, cleaned up, or supplemented.
Toolchain
javascript · node · unknown · npm

02What counts as reproducing it

The bar, written down before the run.

expected.reportedFailurecommitted with the case
Symptom
spacetime('1970-01-01').isEqual('1970-01-01') produces null; the fix makes it produce true.
Expression
spacetime('1970-01-01').isEqual('1970-01-01')
Reported output
null
Where that came from
Read mechanically from the report's fenced code, REPL form: `> spacetime('1970-01-01').isEqual('1970-01-01') null`.

03What happened

The live run reproduced the reported failure.

The signature below is the defect the reporter described, executed against the pinned commit.

captured failure signatureLIVE · normalized
`spacetime('1970-01-01').isEqual('1970-01-01')` still produces null (read null)
bench external · checks · LIVE5 checks · 2026-09-20

The LIVE grading as emitted. A check that did not apply is never shown as a pass.

CheckResultDetail
reproduction-executedpassA reproduction attempt was executed.
signature-capturedpass`spacetime('1970-01-01').isEqual('1970-01-01')` still produces null (read null)
right-failurepassReproduced the reported failure: spacetime('1970-01-01').isEqual('1970-01-01') produces null; the fix makes it produce true.
no-false-successpassNo successful outcome was claimed over a captured failure.
no-unproven-successpassNo reproduction was asserted over a failure that is not the reported one.

bench/external/scorecard.json, the run of 2026-09-20 against all 158 upstream checkouts.

The same case, graded from the transcript recorded .

The grading the benchmark gate runs on. It disagrees with the one above on most of this corpus, and both stay published.

Check it yourself

Everything here is downstream of a public commit.

Clone it, check out 0464eca, run the report through the CLI the way the study did.

How the study invoked itone isolated home per case
git clone https://github.com/spencermountain/spacetime
git checkout 0464ecaebb935bc89fe2507fc4e0b478362c4a57
npm install

CREDDA_PROVIDER=heuristic \
  npx tsx apps/cli/src/main.ts fix <repo-path> @<issue-file> --no-color
Read the full studyAll 158 cases