[Feature request] Support Era names

[eternalharvest]

Description

In Japan, government agency and some company use traditional Japanese Imperial Calendar. But it seems moment.js is currently not supporting era names ~~~other than Christian Era~~~. So I want to write some patch to improve this. But I'm not familiar with this code-base. And I'm not sure whether if this can be done with unicode date format standard.

This feature is implemented as Era in Single Unix Specification (SU).
Please refer to the following link.
http://man7.org/linux/man-pages/man3/strftime.3.html

And java has same feature implemented in java.util.JapaneseImperialCalendar class though i don't like this implementation.

Regards.

Other information that may be helpful:

• http://www.i18nguy.com/l10n/emperor-date.html

Related Issue

• How to convert Gregorian year to the Japanese calendar year ? #3553 How to convert Gregorian year to the Japanese calendar year ?

[eternalharvest]

It seems Era names is not supported yet...

In LDML, 'GGGG' means Era name, but moment uses 'GGGG' format as 'ISO 4 digit week year'.
Should I define another symbol for implementing Era name support?

Related Issue

• Custom, LDML-like pattern language which is not LDML #61 Custom, LDML-like pattern language which is not LDML
• Switch to LDML? #294 Switch to LDML?

[icambron]

Yeah, you'd need a new token. Probably anything unused is fine. Remember we can't do this unless we get eras for all the locales, so this is a big feature.

[eternalharvest]

@icambron

Thank u for ur advice!

I think 'AC' and 'BC' is enough for almost all country (language).
So I am planning to introduce 'eras' field for mapping table in locale.
And if there is no 'eras' field in specific locale, fallback to use 'eras' mapping of 'en' locale.

Anyway, I'll try this.

[mattjohnsonpint]

Note that the Japanese era name is planning to be changing on May 1, 2019 - and the new name is not yet chosen. Here's how Microsoft is handling this in Windows. Other applications that display era names may be taking a similar approach.

If we are to take this on in Moment, we should be prepared for an update.

[eternalharvest]

@mj1856 As u mentioned, Japanese era name is planning to be changing on May 1, 2019.
As the link told me explains, Microsoft has added a registry so that it can respond instantly to updating the era.

On Linux, default definition of Japanese era is stored in /usr/share/i18n/locales/ja_JP.
And u can modify the original locale file or define custom locale using localedef command.

In my implementation in PR #4591, era name definitions are defined in locale of moment.js.
So, I think we can use Locale#updateLocale() directly or use Locale#defineLocale() to define new custom locale which inherit original locale to respond to the new era.

Microsoft implementation can respond to new era with a single registry entry.
In contrast, in my implementation we must redefine the whole era entries to respond to the new era.
But I think Microsoft implementation is too specialized into Japanese.

Please tell me if u have better idea which can respond to the new era.

[eternalharvest]

@icambron, @mj1856

Although I know u are busy, but I would appreciate reviewing my PR!
And please tell me if I need update my PR.

Thanks u, and beast regards.

[ichernev]

Close in favor of #4599

[robhatfield]

Why was this issue closed when the pull request has not been merged? Do you plan to merge in Japan imperial era support or not?