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…hour12 duplication Fixes #4535 This commit addresses two issues with FormattedDateTimeRange: 1. **H24 midnight rendering**: Same-day ranges starting at midnight (e.g., 00:00-00:45) were incorrectly showing "24:00-24:45" instead of "00:00-00:45". Root cause: The condition !rangeFormatOptions?.isDifferentDate meant "convert 0→24 when NOT in a range with different dates". Same-day ranges have isDifferentDate:false, causing unwanted conversion. Fix: Changed to !rangeFormatOptions (undefined check), so 0→24 conversion only happens in non-range single-date formatting. 2. **Date duplication with hour12**: When hour12:true, date/day were duplicated for any time range (e.g., "Wed, 18 Feb 2026, 7:00 am – Wed, 18 Feb 2026, 4:00 pm" instead of showing date once). Root cause: CLDR data synthesis fallback to alternate hour cycles (12hr ↔ 24hr) only checked if timeIntervalFormats was undefined or not an object, missing the case where it's an empty object {}. Fix: Added Object.keys().length === 0 check to properly trigger fallback when interval formats are empty, ensuring 12-hour skeletons can use 24-hour interval patterns during data generation. Co-authored-by: Long Ho <longlho@users.noreply.github.com>
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Fixes #4535
Summary
This PR fixes two bugs in
FormattedDateTimeRangethat were causing incorrect formatting:hour12: trueChanges
Bug 1: H24 Midnight Rendering
Root Cause: The condition
!rangeFormatOptions?.isDifferentDatemeant "convert 0→24 when NOT in a range with different dates". Same-day ranges haveisDifferentDate: false, causing unwanted conversion.Fix in
FormatDateTimePattern.ts:if (v === 0 && !rangeFormatOptions?.isDifferentDate)if (v === 0 && !rangeFormatOptions)Example:
Sun, 3 May 2026, 24:00–24:45Sun, 3 May 2026, 00:00–00:45✓Bug 2: Hour12 Date Duplication
Root Cause: CLDR data synthesis fallback to alternate hour cycles (12hr ↔ 24hr) only checked if
timeIntervalFormatswas undefined or not an object, missing the case where it's an empty object{}.Fix in
extract-dates.ts:Object.keys(timeIntervalFormats).length === 0checkExample:
Wed, 18 Feb 2026, 7:00 am – Wed, 18 Feb 2026, 4:00 pmWed, 18 Feb 2026, 7:00 am – 4:00 pm✓Tests
Added 3 comprehensive test cases:
Breaking Changes
None. These are bug fixes that make behavior match user expectations and LDML specifications.
Note: The fix to
extract-dates.tsrequires regenerating locale data before merging.Generated with Claude Code