[threeten-dev] Julian and Ethiopian calendar system

[yoshito_umaoka at us.ibm.com]

> Hi Yoshito,
> Does LDML have any "ca" code for the Julian calendar system? I cannot
> see one in http://unicode.org/repos/cldr/trunk/common/bcp47/calendar.xml
> I'd like to add a class representing the Julian calendar system at
> some point, and it should really have a "ca" code, hopefully "julian".
> It would only need localization for the calendar system name, as the
> other text (months/day-of-week/era) would be the same as the "gregory"
> calendar.
> (Note that I presume the "gregory" calendar is proleptic, applying the
> same rules back into far history)

CLDR was originally spawned from ICU project long time ago. It's 
independent from ICU project now, so it is not necessarily follow the 
original ICU model. In ICU, Gregorian calendar is not always proleptic. By 
default, it uses 1582-10-15 as the switch date between Julian and 
Gregorian. The implementation was contributed to JDK - therefore, 
java.util.GregorianCalendar also use the same logic (see 
GregorianCalendar#setGregorianChange).

Strictly speaking, ICU/JDK GregorianCalendar might be called 
WesternCalendar or something - because it's hybrid. I'm not sure there is 
convincing reason to add "Julian". This might also fall into calendar 
"variant" category.
> 
> Has any thought been given to converting the two ethiopian calendar
> systems to be "cv" variants? "ethioaa" and "ethiopic" are variants of
> the same calendar system AFAICT.

Good point. It might make sense. Although they require different symbols 
for era (has impacts to format symbol data unlike Islamic variants). 
Because we invented "cv" for supporting Islamic requirements recently, we 
did not have chance (or urgent needs) to see if this concept is applicable 
to others yet. I'll bring these topics to CLDR TC, but I assume these are 
not urgent. For now, CLDR project folks are busy on shipping CLDR 23 - so 
this is something we would consider after CLDR 23.

Thanks,
Yoshito