<i18n dev> RFR: 8317742: ISO Standard Date Format implementation consistency on DateTimeFormatter and String.format [v5]

[Roger Riggs]

On Tue, 7 Nov 2023 13:45:54 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> test/jdk/java/util/Formatter/BasicDateTime.java line 473:
>> 
>>> 471:                 "%tF",
>>> 472:                 DecimalFormatSymbols.getInstance(localeEuES).getMinusSign() + "2023-01-13",
>>> 473:                 LocalDate.of(-2023, 1, 13));
>> 
>> Needs some comments here, otherwise it would be a bit cryptic. Also, "eu-ES" locale using `\u2212` depends on the current CLDR implementation, so you might want to check all locales with  `Locale.availableLocale()`.
>
> While it might be reasonable to localize using `getMinusSign()` this will introduce a new inconsistency with `DateTimeFormatter` (which *does not* localize minus signs in front of years): 
> 
> int minus = DecimalFormatSymbols.getInstance(Locale.forLanguageTag("eu-ES"))
>     .getMinusSign()
> minus ==> 8722
> 
> int first = DateTimeFormatter.ISO_DATE
>     .withLocale(Locale.forLanguageTag("eu-ES"))
>     .format(ZonedDateTime.now()
>     .minus(4000, java.time.temporal.ChronoUnit.YEARS)
>     .charAt(0)
> first ==> 45

Within java.util.Formatter, the year formatter supports only the range [0,9999].
Only ISO_STANDARD_DATE has a ISO 8601 format defined for numbers outside that range. 
The formatting in java.time is defined over the full range of years.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16033#discussion_r1385067362