For Project Online, the most reliable way I found to fix it was to manually edit the URL to replace en-US with en-AU, then bookmark that.
To make matters worse, randomly, employees will have their OS using US or GB locales so that if you distribute a CSV, it will work for some employees, but not for others.
Open control-panel for regional settings, select "Advanced settings" button on the bottom control.exe intl.cpl
If you don't know any of these problems, then all the people and systems you work with have a "." as decimal and "," as separator, and you are spared from the hell of MS Office being unable to overrule these OS-settings when treating a CSV
Thing is, it is not about what you used, you are not able to control this from happening when your CSV should work for people in other countries. Whatever configuration you used which never got a complain, if your recipients also used Excel to work with those documents, they probably have the same regional setting on Windows for list/thousands/decimal separator.
If you use ";" as separator, i.e. Excel in UK, US, Japan, China, Korea will not be able to correctly open your CSV.
But even better: If you created this CSV on a France or Sweden regional setting, the thousands separator will be a whitespace ("1 000" instead "1,000" or "1.000"), so Excel in e.g. Italy will not detect those properly.
> I am surprised this is problem enough (in 2025) that people emotionally discuss it.
It is a (intentional) weakness of MS Office for those who work in an international environment, because Excel links itself to .csv files to hinder the experience, as it is neither able to properly detect them nor guide their users through a process to properly handle them.
1.01, "hi", CSV has problems, "1.01"
1,01, "hi", Yes it really does, "1,01"
See the problem now?Your operating system cannot solve this problem.
It's not about people, it's about the Windows locale setting and how MS Excel interprets a CSV-file when you doubleclick it