Sorry, Marc. That's just not true. As I explained it above, and later linked to an analogous case, I would need to switch to US locale. But this would change other things, such as commas and periods in numbers and currency, and even formula functions will change in some languages.
When the dates are in US format, they are misinterpreted in other regions. Up to the 12th in the month, the month and date are swapped in interpretation; from the 13th onwards,* the date is not understood as a date at all and considered to be general data. If it goes into another month, it will swap again, and again. But will never interpret any of the dates correctly.
* Because there are only 12 months.
If the user recognises the problem and understands the cause, it can be worked around. But it creates more work. Using the international date format removes all the complications. And from that (because that date format is understood by Excel in all locales), it extremely easy to switch between date conventions for selected cells (because all the data is correctly interpretted in the first place).