Invalid dates in Japanese eras?

Kip Cole kipcole9 at
Thu Sep 9 04:42:25 CDT 2021

Ahhh, thank you so much - that makes sense to me. Here was I thinking about “y" from a formatting point of view. So basically “extended year” would mean “proleptic Gregorian year” for the given date in any calendar?

Very helpful, and makes sense (and hopefully is even correct!)

Regards, —Kip

> On 9 Sep 2021, at 5:39 pm, Edward Welbourne <edward.welbourne at> wrote:
> Wáng Yifán (09 September 2021 05:07) wrote:
>> [...] I couldn't find the exact definition of "extended Gregorian year" elsewhere.
> My semi-educated guess is that "extended Gregorian year" means the year
> that the relevant date would fall in, in the "extended Gregorian
> calendar" - i.e. the Gregorian calendar extrapolated backwards, if
> necessary, to before Gregory introduced it.
> 	Eddy.

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