This fixes issues with some locales where "system default" is the default setting for times and dates. This happens, for example, when using German (Austria) as a locale in Windows, or when setting it manually in Excel.
Especially when languages such as German (Austria) are used, where the "system default" is used for such types, the user is not aware of the locale and the probability of creating an Excel file that cannot be loaded by XLNT is very high.
Explanation: https://bz.apache.org/ooo/show_bug.cgi?id=70003
This fixes issues with some locales where "system default" is the default setting for times and dates. This happens, for example, when using German (Austria) as a locale in Windows, or when setting it manually in Excel.
Especially when languages such as German (Austria) are used, where the "system default" is used for such types, the user is not aware of the locale and the probability of creating an Excel file that cannot be loaded by XLNT is very high.
This pull request fixes this issue.