Custom export format biblatex date field to bibtex year, month and day ones.

[webanck]

Hello, I see date processing is still in the pipes ! (See issues #1249 and #6224)

Almost two years ago (see here), I asked for a way to write a custom export with dates from the biblatex date field to bibtex year, month and day fields with an emphasis on the month field (I am not the first one, see here).
I tried using the DateFormatter but an error is still raised when the date field doesn't resolve as a full ISO date (YYYY-MM-DD), and even if it worked, it would only output the month number, and not the bibtex equivalent.

Any clue on how to solve this ?

[webanck]

Well, in fact, it is very easy to solve now as all fields seem well treated as valid aliases now.

The custom export filter as

\begin{year}  year = \year\end{year}\begin{month},
  month = \month\end{month}\begin{day},
  day = \day\end{day}

will now output entries as

  year = 2018,
  month = May,

[webanck]

Well, in fact, it only works for the month of May because it is already a 3 characters long string, but for January for instance, the full month name will be output, instead of Jan.
So my initial problem is still not solved :(
There is no formatter documented to output the month in the same format as the bibtex field !
Even the undocumented RisMonth format makes the assumption of a short name for the month.

[Siedlerchr]

Have you seen the DateFormatter? https://docs.jabref.org/collaborative-work/export/customexports#built-in-export-formatters

edit// I saw that it requires valid iso date.

[webanck]

Yeah, I tried but it doesn't work, as you saw (I added an explicit mention about it in the first message of this issue).

[Siedlerchr]

I currently see no existing solution, so you would need to write your own Formatter which can format Months.
/Edit: That should not be that difficult as we already have a Month class which is able to do some month parsing and probably formatting as well.

[Siedlerchr]

Thanks to @joethei there's now a new Short Month Formatter

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