Export: Use YYYY-MM-DD format for check-in CSV-export (Z#23115722)

[wiffbi]

No description provided.

[codecov]

Codecov Report

Merging #3082 (8ee97a2) into master (7b301b6) will not change coverage.
The diff coverage is 0.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3082   +/-   ##
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  Coverage   78.36%   78.36%           
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  Files         403      403           
  Lines       54277    54277           
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  Hits        42533    42533           
  Misses      11744    11744           

Impacted Files	Coverage Δ
src/pretix/plugins/checkinlists/exporters.py	56.91% <0.00%> (ø)

[raphaelm]

Hmm. I'm undecided here. We use localized dates in most exports, such as also the invoice exporter, to make them more readable. If we decide it's the right thing to do, we could change them across the board, but we might break some customer's process with it.

We could try moving the formatting up a layer into the ListExporter/MultiSheetListExporter classes. That way, we could handle it differently for Excel (using a native date format?) and for CSV, if we think that'd be better (not sure about that).

[wiffbi]

I like the idea of using a native date format in excel! Regarding localized dates in CSV, I think machine readable dates would also help here, as CSV lends itself to automated machine processing even more than xls. So I think I am more in the camp „no localized dates at all“ in data exports (except maybe PDF?). I think if we have localized dates with native date format in excel, that would make it the readable export and CSV with YYYY-MM-DD would make it easier to process with automation.

Regarding this PR: currently in this export, order date is formatted as YYYY-MM-DD – so differs from check-in, check-out and subevent.date.