feat: add %F and %u strftime format codes

[Koan-Bot]

What

Add two missing POSIX strftime format specifiers: %F (ISO 8601 date) and %u (Monday-based weekday number).

Why

%F and %u are defined in POSIX.1-2001 and widely expected by users coming from C's strftime or GNU coreutils date. Currently, time2str("%F", time) silently returns the literal "F" instead of a date — surprising behavior for a standard code.

How

• format_F: composite format returning %Y-%m-%d (same pattern as existing format_D, format_T)
• format_u: returns $_[0]->[6] || 7 — maps Sunday from Perl's 0 to POSIX's 7
• Fixed %e documentation range from 1..32 to 1..31

Testing

15 new test cases in t/format.t (292 → 307):

• %F and %u tested across all 6 language sections (English, German, French, Italian, Bulgarian, Portuguese)
• Dedicated Sunday boundary test verifying %u returns 7 and %w returns 0
• Full test suite passes

[atoomic]

@Koan-Bot rebase

[greptile-apps]

Greptile Summary

This PR adds two POSIX strftime specifiers — %F (ISO 8601 date: YYYY-MM-DD) and %u (Monday-based weekday: 1–7) — that were previously unimplemented and silently fell back to returning the bare letter. Both are implemented in Date::Format::Generic and are inherited by all language subclasses via the existing Date::Language → Date::Format::Generic chain, so no per-language copies are needed. The %e documentation fix (1..32 → 1..31) is also correct.

Confidence Score: 5/5

Safe to merge — implementation is minimal, follows existing patterns exactly, and is thoroughly tested.

Both new format functions are correct: format_u uses the idiomatic $_[0]->[6] || 7 pattern to remap Sunday from 0 to 7, and format_F composes existing helpers the same way format_D and format_T do. Inheritance means all 30+ language subclasses get the new codes for free. 15 new test cases cover every language fixture plus a dedicated Sunday boundary check. No P0 or P1 findings.

No files require special attention.

Important Files Changed

Filename	Overview
lib/Date/Format/Generic.pm	Adds format_u (Monday-based weekday, Sunday→7) and format_F (ISO 8601 YYYY-MM-DD); both follow existing patterns and are correctly implemented.
lib/Date/Format.pm	Documentation additions for %F and %u, plus correction of %e range from 1..32 to 1..31.
t/format.t	Adds 15 new test cases covering %F and %u across all 6 language sections plus a dedicated Sunday boundary test (315964800); test count updated from 292 to 307.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["time2str / strftime call"] --> B["_subs() regex substitution\n%(O?[%a-zA-Z])"]
    B --> C{Format code?}
    C -->|"%F"| D["format_F()\nformat_Y . '-' . format_m . '-' . format_d\n→ YYYY-MM-DD"]
    C -->|"%u"| E["format_u()\n$_[0]->[6] || 7\n→ 1..7, Sunday=7"]
    C -->|"%w"| F["format_w()\n$_[0]->[6]\n→ 0..6, Sunday=0"]
    C -->|"%D"| G["format_D()\nformat_m . '/' . format_d . '/' . format_y\n→ MM/DD/YY"]
    C -->|"unknown"| H["return bare letter\n(fallback)"]

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_{Reviews (1): Last reviewed commit: "feat: add %F (ISO 8601 date) and %u (Mon..." | Re-trigger Greptile}

[Koan-Bot]

Rebase with requested adjustments

Branch koan.atoomic/add-missing-format-codes was rebased onto main and review feedback was applied.

Stats

3 files changed, 22 insertions(+), 2 deletions(-)

Actions performed

• Already-solved check: negative (confidence=high, reasoning=None of the recent commits on main mention %F, %u, format_F, or format_u — the ISO 8601 date format )
• Resolved merge conflicts (1 round(s))
• Rebased koan.atoomic/add-missing-format-codes onto upstream/main
• Pre-push CI check: previous run passed
• Force-pushed koan.atoomic/add-missing-format-codes to origin
• CI check enqueued in ## CI (async)

CI status

CI will be checked asynchronously.

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Automated by Kōan

[atoomic]

do not bump/pin the version for cpm let's use install-with-cpm@v2 instead

[atoomic]

@Koan-Bot rebase

[Koan-Bot]

Rebase with requested adjustments

Branch koan.atoomic/add-missing-format-codes was rebased onto main and review feedback was applied.

Changes applied

• Removed pinned version: "0.997016" for cpm and upgraded install-with-cpm@v1 to install-with-cpm@v2 per reviewer request to not bump/pin the cpm version and use v2 of the action instead.

Stats

4 files changed, 23 insertions(+), 3 deletions(-)

Actions performed

• Already-solved check: negative (confidence=high, reasoning=None of the recent commits on main mention %F, %u, or ISO 8601 date format codes — the feature this )
• Rebased koan.atoomic/add-missing-format-codes onto upstream/main
• Applied review feedback
• Pre-push CI check: previous run passed
• Force-pushed koan.atoomic/add-missing-format-codes to origin
• CI check enqueued in ## CI (async)

CI status

CI will be checked asynchronously.

---

Automated by Kōan