Editorial: Be explicit about the Gregorian to Meiji switchover month and day in the Japanese calendar #86
Description
Even in the post-PR #79 form, the text about the eras in the Japanese calendar says:
Imperial era names only extend as far back as the Meiji period (starting in ISO year 1868) during which calendar reforms took place.
which states the ISO year but not the month and day within the ISO year. This week, I've spent enough time trying to make sense what's a bug and what's not a bug on that point that given that there was a long-standing CLDR bug on this point that has propagated widely in observable software, I think it would be practically useful to explicitly state the first ISO day that this spec expects to count as being in the Meiji era.
I suggest making it explicit that this spec intends the ISO day 1868-10-23 to be the first day that computes into the Meiji era (and, therefore, 1868-10-22 and earlier ISO days to use one of the Gregorian eras).
(I'm aware that this would be restating something that #79 delegates to CLDR, but the current mention of the year is already a restatement. I'm OK with phrasing the restatement in a way that theoretically wouldn't be a normative statement if there's concern about precedence of this spec vs. CLDR.)