[threeten-dev] 2 digit year -> year date conversions for non-ISO calendars

[Roger RIggs]

Hi,

The behavior of the parser for 2 digit years does not work as expected
for non-ISO calendars.  Due to the definition in DateTimeFormatterBuilder
of the "yy" pattern as being based on the year 2000 it only works for
The ISO and GregorianCalendars;  but for the ThaiBuddhistCalendar
with the year offset and for the HijrahCalendar it produces dates that
do not resolve correctly and causes an exception.

For example,

         Chronology chrono = ThaiBuddhistChronology.INSTANCE;
         Locale locale = Locale.getDefault(Locale.Category.FORMAT);

         String pattern = "M/d/yy G";
         DateTimeFormatter df
                 = new DateTimeFormatterBuilder().appendPattern(pattern)
                 .toFormatter()
                 .withChronology(chrono);

         ThaiBuddhistDate expected = 
ThaiBuddhistChronology.INSTANCE.date(ThaiBuddhistEra.BE, 2576, 10, 29);
         String input = "10/29/76 B.E.";

         parsed = df.parse(input);
         ThaiBuddhistDate actual = ThaiBuddhistDate.from(parsed);
         System.out.printf("pattern=%s, input=\"%s\", date=%s, TB date: 
%s%n", pattern, input, parsed, actual);

The output is:
pattern=M/d/yy G, input="10/29/76 B.E.", date={},ThaiBuddhist,null 
resolved to ThaiBuddhist BE 2076-10-29,null, TB date: ThaiBuddhist BE 
2076-10-29
Expected: ThaiBuddhist BE 2576-10-29
Actual:   ThaiBuddhist BE 2076-10-29

See JBS issue:

  * JDK-8024076 <https://bugs.openjdk.java.net/browse/JDK-8024076>
    Incorrect 2 -> 4 year parsing and resolution in DateTimeFormatter

Roger