The first year of Japanese calendar era should use 元 instead of numeric 1.
added "spellout-numbering-year" to support this behavior, but this is not used by default format pattern.
I propose to change the default date format pattern for Japanese calendar in Japanese locale to use the RBNF rule for year number.
OK, in "ja" locale, implemented this for the japanese-calendar standard full/long/formats (I think in TC meeting we discussed not doing it for the short format like H1/1/8, but we can revisit if necessary). This uses the new jpanyear numbering system value added in :