date: expand GNU-compatible parsing and formatting

[anastygnome]

Handle extended years, epoch seconds, normalization, DST gaps, and strftime modifier precedence

Refs #14705

Closed or superseeds :
Closes #14648
Closes #14649
Closes #9253
Closes #12954
Closes #12944
Closes #12034
Closes #12897
Closes #11657
Closes #11658
Closes #9275
Closes #11752
Closes #14179
Closes #11778
Closes #12064

Unit test ignore removed (may need a backport):
Refs uutils/parse_datetime#279
Refs uutils/parse_datetime#280

[codspeed]

Merging this PR will degrade performance by 12.56%

⚠️ 2 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• complex_relative_date
• single_date_now

❌ 5 regressed benchmarks
✅ 7 untouched benchmarks
⏩ 444 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	file_custom_format	30 ms	36.5 ms	-17.9%
❌	Simulation	file_iso_dates	31.5 ms	38.2 ms	-17.52%
❌	Simulation	file_localized_names	41.9 ms	48.6 ms	-13.73%
❌	Simulation	file_tz_abbreviations	35.4 ms	38.1 ms	-7.07%
❌ ⚠️	Simulation	complex_relative_date	292.6 µs	310.8 µs	-5.84%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing anastygnome:test-util (a197690) with main (e6eb5ad)²}

Footnotes

1. 444 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (09a1ec1) during the generation of this report, so e6eb5ad was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[anastygnome]

extra work => additional cost.

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/date/date is no longer failing!
Congrats! The gnu test tests/date/date-tz is no longer failing!

[anastygnome]

CICD and Android are related to tail/cp, nothing related to this PR

[sylvestre]

sorry, but we can't take this: emit_gnu_debug hardcodes the expected output for specific GNU test inputs, which doesn't fix anything and looks taken from the GNU tests. If you want to keep going, please split it into small PRs that fix real behavior, one at a time.

[anastygnome]

@sylvestre would making the non debug tests into one PR be ok?

[sylvestre]

just the tests or tests+fixes?

[anastygnome]

I mean the code & test that fix tests/date/date & date/date-tz are very similar (I blieve matching debug output isn"t really wise but I had matched it to see if we could and discuss it here

[sylvestre]

Sure but this pr is huge. I would prefer smaller changes

[anastygnome]

I reduced the scope @sylvestre

[anastygnome]

@cakebaker @xtqqczze if one od you may review this it'd be appreciated

[cakebaker]

I'll likely wrap up the review tomorrow. The tests look fine.

[anastygnome]

No issues, take your time, I'll wait

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[anastygnome]

How does this PR relate to #11778 and #12064?

If this PR is intended to supersede those PRs, please mention them in the PR description using GitHub's closing keywords.

done

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[anastygnome]

@sylvestre can we merge this as is?

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[cakebaker]

Congrats! The gnu test tests/date/date is no longer failing!
Congrats! The gnu test tests/date/date-tz is no longer failing!

Kudos and thanks!

[anastygnome]

@cakebaker I have fixed 3 other issues as a spin-off PR, incoming tonight

[xtqqczze]

Congrats! The gnu test tests/date/date is no longer failing!
Congrats! The gnu test tests/date/date-tz is no longer failing!

@cakebaker #14705 needs updating

[cakebaker]

@xtqqczze done, thanks for the hint!

[xtqqczze]

Closes #13818?

[anastygnome]

So many things I can't keep up with

[xtqqczze]

Well done, I think that may be a record for number of issues closed with one PR!

[SichenLiang]

I think this also changed %F with a flag or width for years below 1000. GNU still applies the flag to the year inside %F; the gnulib change only stopped that for %D, as discussed in #11657. Main matched GNU before this PR:

$ TZ=UTC LC_ALL=C date -d 0001-01-01 +%-F
1-01-01

After the merge, main prints 0001-01-01. The same happened with %_F and widths such as %6F. %0F and %+F were already different from GNU before this PR.

[anastygnome]

@SichenLiang will address this in my current PR. Regression introduced by a lacking coverage