Created attachment 161605 [details]
Example file from Excel

Attached example document was made in Excel, I entered some dates in the 05-10 06-12 etc. format. Excel recognized this and set the cell type to Date with DD-MMM format, so that it appears as: day.mon (month is localized and abbreviated). Format code is nn.hhh (or DD.MMM in English).
This format is imported incorrectly in Calc, depending on locale:
- With en-US it appears as D-MMM so that separator is dash instead of dot (no big deal, just interesting)
- With hu-HU it appears as DD.MMM but here the month appears with Roman numerals instead of the abbreviated form.

I also added a chart with the example values as data row labels and upon import all X axis labels are now 1-XII and the drawn line is completely broken.

Steps to reproduce:
    1. Open attached document and observe date format differences in A2:A5)

Actual results:
Roman numerals instead of abbreviated localized month name.

Expected results:
Abbreviated localized month name, just like in Excel.

LibreOffice details:
Version: 7.1.0.0.alpha0+ (x64)
Build ID: 68095e63a8ad8f6079b15e475179a14a64da36d3
CPU szálak: 4; OS: Windows 6.3 Build 9600; Felületmegjelenítés: Skia/Raster; VCL: win
Locale: hu-HU (hu_HU); UI: hu-HU
Calc: CL

Also happens in:
Verzió: 6.0.0.3
Build az.: 64a0f66915f38c6217de274f0aa8e15618924765
CPU szálak: 4; OS: Windows 6.3; Felületmegjelenítés: alapértelmezett; 
Területi beállítások: hu-HU (hu_HU); Calc: CL

Version: 5.0.0.5
Build ID: 1b1a90865e348b492231e1c451437d7a15bb262b
Locale: hu-HU (hu_HU)

Verzió: 4.0.0.3 (Build az.: 7545bee9c2a0782548772a21bc84a9dcc583b89)