Document that the Japanese calendar is currently broken in browsers for dates before 1868-10-23 #41420
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…r dates before 1868-10-23
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(comment last updated: 2025-10-09 16:54:09) |
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Side note: This calendar was taken into use on 1873-01-01, so the bug only affects proleptic dates. |
hsivonen
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Josh-Cena
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Oct 7, 2025
| | `islamic-civil` | Hijri calendar, tabular/rule-based with leap year rule II (leap years 2,5,7,10,13,16,18,21,24,26,29 in the 30-year cycle (1-based numbering)) and Friday/civil epoch (July 16, 622 Julian / 0622-07-19 ISO) | | ||
| | `iso8601` | ISO calendar (variant of the Gregorian calendar with week rules and formatting parameters made region-independent) | | ||
| | `japanese` | Japanese Imperial calendar (this calendar adds an era for each new emperor, so the output year and era for a future date may not match the input year and era when your code runs on a future engine version) | | ||
| | `japanese` | Japanese Imperial calendar (this calendar adds an era for each new emperor, so the output year and era for a future date may not match the input year and era when your code runs on a future engine version. **Note:** As of October 2025, dates prior to 1868-10-23 ISO don't work correctly in browsers due to a CLDR bug.) | |
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IMO this isn't particularly helpful (what does "don't work" mean?) and I understand you are trying to make the text succinct. Can we move this into a note after the table, and inline the link rather than presenting it as a reference?
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I added longer remarks after the table and said more specifically what the behaviors that don't match the current spec proposal are.
Josh-Cena
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Oct 8, 2025
files/en-us/web/javascript/reference/global_objects/intl/supportedvaluesof/index.md
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Co-authored-by: Joshua Chen <sidachen2003@gmail.com>
Josh-Cena
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…rtedvaluesof/index.md
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Description
Adds a note that the Japanese calendar doesn't actually at present work correctly in browser for dates before 1868-10-23.
Motivation
Helps readers avoid triggering a cross-browser bug.
Additional details
See https://unicode-org.atlassian.net/browse/CLDR-11375 (linked from the text of the PR) for the bug that causes all browsers to have incorrect data for the start of the Meiji era.
Also, see https://tc39.es/proposal-intl-era-monthcode/ , which requires browsers to use Gregorian eras for the Japanese calendar for dates before the Meiji era.