Support the CLDR 49 ordinal day of month pattern field by summeriver13 · Pull Request #1383 · python-babel/babel

summeriver13 · 2026-10-12T10:29:27Z

scripts/import_cldr.py aborts on the CLDR 49 data with ValueError: Invalid length for field: 'ddd' (babel/dates.py:1809): CLDR 49 uses ddd for ordinal days of the month
("Sept 13th"), which the d field did not accept.

Changes

babel/dates.py: accept ddd for d and format the ordinal day picked by
Locale.ordinal_form; locales without ordinal forms fall back to a single d as the CLDR
spec prescribes, so the day is not zero-padded.
babel/core.py: new Locale.ordinal_day_formats property (CLDR 49 <dayOfMonth> patterns
by ordinal plural category, {0} replaced by the day).
scripts/import_cldr.py: import dayOfMonths for the gregorian calendar
(dayOfMonthContext[@type="format"] / dayOfMonthWidth[@type="abbreviated"]), plus tests
for parsing, the ordinal output and the fallback.

Verification

$ uv run python scripts/import_cldr.py <cldr-49-beta2>/common   # exit 0, 0 errors, 183 locales
$ uv run python -c "from datetime import date; from babel.dates import format_date as f; print(f(date(2026, 9, 13), 'MMM ddd, y', locale='en'))"
Sep 13th, 2026

uv run pytest -q on the pinned CLDR 48.2 data: 7875 passed, 10 skipped, 2 xfailed.
The new tests fail without the code change, with exactly the ValueError from the issue.

I left the second half of #1379 (cldr-exemplars-delta import) to the maintainers.

Disclosure: written with AI assistance; I reviewed the diff, ran the importer and the suite.

akx · 2026-11-05T08:05:44Z

@summeriver13 #1427 was just merged, so we are on CLDR 49. Could you rebase this?

summeriver13 · 2026-11-05T10:56:11Z

Rebased onto master (b33ab76, CLDR 49). #1427 already added ddd to PATTERN_CHARS, so that hunk dropped out. The remaining change is the formatting semantics: ddd used to zero-pad the day to three digits (001); it now uses the locale's <dayOfMonths> patterns and falls back to a single d when the locale has none. scripts/import_cldr.py imports those patterns.

codecov · 2026-11-05T11:18:51Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.67%. Comparing base (b33ab76) to head (870cceb).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1383      +/-   ##
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  Lines        4972     4982      +10     
==========================================
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  Misses        315      315

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codspeed · 2026-11-05T11:19:34Z

Merging this PR will not alter performance

✅ 88 untouched benchmarks

_{Comparing summeriver13:fix/ordinal-day-of-month-ddd (870cceb) with master (b33ab76)}

Copilot

🟢 Approval recommended

The ordinal day-of-month support changes have no active review issues blocking approval.

No open issues 🎉

What changed in this PR

Adds CLDR 49 ordinal day-of-month support to Babel’s locale-data importer and date formatter, addressing the ordinal-field portion of #1379. The separate locale migration issue remains out of scope.

Changes:

Imports ordinal day patterns and exposes them through Locale.ordinal_day_formats.
Formats ordinal days using locale plural rules, falling back to an unpadded day when no matching pattern exists.
Adds tests for ddd parsing, ordinal output, fallback behavior, and unsupported field lengths.

File	Description
`tests/test_dates.py`	Tests ordinal day parsing, formatting, and fallback behavior.
`scripts/import_cldr.py`	Imports abbreviated ordinal day patterns from calendar data.
`babel/dates.py`	Adds locale-aware ordinal day formatting.
`babel/core.py`	Exposes ordinal day patterns through a new locale property.

_{Review effort: Balanced}

akx

Small test changes -- and we'll see if other changes are needed once CI rolls through.

summeriver13 · 2026-11-05T11:26:53Z

Done in 1ae0152:

removed test_parse_pattern_ordinal_day and test_parse_pattern_rejects_unsupported_day_length.
test_format_ordinal_day_of_month now formats with the imported en data instead of monkeypatching. The fallback test already used the real de data.

Local run with CLDR 49 data: tests/test_dates.py + tests/test_core.py 2541 passed, 2 xfailed; doctests 176 passed; ruff check clean. With CLDR 48 data the ordinal test fails on Feb 1, 2016, as expected.

akx

LGTM. @tomasr8 if you have a moment to also check this, that'd be grand!

tomasr8 · 2026-11-05T13:25:02Z

I have a few nits, if you give me a few hours I'll post my review :)

tomasr8

A few nits, but otherwise LGTM :)

CLDR 49 adds the "ddd" pattern field for ordinal days of the month ("Sept 13th") and the matching <dayOfMonths> data. PATTERN_CHARS already accepts "ddd", so formatting "ddd" zero-padded the day to three digits ("001"). "ddd" now formats the day with the locale's ordinal forms, keyed by the ordinal plural category, and falls back to a single "d" for locales that have none, as the CLDR spec prescribes. scripts/import_cldr.py imports the dayOfMonth patterns. Refs python-babel#1379

Remove the CLDR version note from the property docstring. Document the format character count. Warn on unsupported CLDR element types. Extend the tests to French and the fallback path. Co-Authored-By: pi <noreply@pi.dev>

akx added the AI Assisted label Oct 13, 2026

tomasr8 mentioned this pull request Nov 3, 2026

Support CLDR 49 #1427

Merged

akx added area/CLDR area/dates labels Nov 5, 2026

summeriver13 force-pushed the fix/ordinal-day-of-month-ddd branch from dfc62a0 to 98659e8 Compare November 5, 2026 10:55

akx requested review from akx and tomasr8 and a balanced review from Copilot November 5, 2026 11:17

Copilot started reviewing on behalf of akx November 5, 2026 11:18

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Comment thread tests/test_dates.py Resolved

Comment thread tests/test_dates.py Resolved

summeriver13 force-pushed the fix/ordinal-day-of-month-ddd branch from 98659e8 to 1ae0152 Compare November 5, 2026 11:26

akx approved these changes Nov 5, 2026

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Comment thread babel/core.py Resolved

Comment thread babel/dates.py Resolved

Comment thread scripts/import_cldr.py Resolved

Comment thread scripts/import_cldr.py Resolved

Comment thread tests/test_dates.py Resolved

Comment thread tests/test_dates.py Resolved

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akx enabled auto-merge (squash) November 6, 2026 07:16

summeriver13 and others added 2 commits November 9, 2026 16:48

Address review comments on ordinal day support

b2b25e6

Remove the CLDR version note from the property docstring. Document the format character count. Warn on unsupported CLDR element types. Extend the tests to French and the fallback path. Co-Authored-By: pi <noreply@pi.dev>

akx force-pushed the fix/ordinal-day-of-month-ddd branch from 870cceb to b2b25e6 Compare November 9, 2026 14:49

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