Description:
In LibreOffice Calc 5.4.5.1 with locale fr-BE, when editing an XLS file, the formula for formatting a date in a cell with TEXT function must be written TEXTE(DATE(2018;3;28);"aaaamm") when function name translation is not disabled (which is the default). The equivalent English formula is TEXT(DATE(2018,3,28),"yyyymm").

However, when saving this to a file and reading it with Apache POI library (https://poi.apache.org/), the persisted formula is TEXT(DATE(2018,3,28),"aaaamm") which is OK except for the format string that has not been translated into "yyyymm".

Using directly the English format code ("yyyymm") prevents the date to be properly formatted in LibreOffice but leads to the persistence of the right formula in the file.

I would expect that:

1. TEXTE(DATE(2018;3;28);"aaaamm") (or whatever internationalized equivalent) is properly persisted as TEXT(DATE(2018;3;28);"yyyymm")
2. Disabling function name translation also disables format code translation (i.e. "yyyymm" becomes a valid format code)

Note that a possible workaround is to change the locale of LibreOffice to English via Menu > Options > Language Settings.

Steps to Reproduce:
1. In LibreOffice Calc 5.4.5.1 with fr-BE locale, format a date using TEXT function e.g. TEXTE(DATE(2018;3;28);"aaaamm") or TEXT(DATE(2018;3;28);"aaaamm") without function name translation.
2. Save the file
3. Change LibreOffice locale to en-US
4. Open the file and see that formatting does not work as expected

Actual Results:  
Cell contains text Wednesday01

Expected Results:
Cell should contain text 201803


Reproducible: Always


User Profile Reset: No



Additional Info:
Version: 5.4.5.1
Build ID: 1:5.4.5-0ubuntu0.17.10.5
Threads CPU : 4; OS : Linux 4.13; UI Render : par défaut; VCL : gtk3; 
Locale : en-US (fr_BE.UTF-8); Calc: group


User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:59.0) Gecko/20100101 Firefox/59.0