The format date DD.MM.YYYY in the .xlsx Calk files in the Microsoft Office looks like MM.DD.YYYY.
A sample please, and possibly screenshots - upload to a public share and post links by editing your question
That bug was fixed https://bugs.documentfoundation.org/show_bug.cgi?id=113889 in LO 5.4.4.
What is your version of LibreOffice?
If the language in Calc is set to English (USA), then the default date format will be month-day-year, MM.DD.YYYY, because USA. If you click Format → Cells… and go to the Numbers tab, you can either change the language to get a different date format, or enter the Format code manually, e.g. DD.MM.YYYY or whatever you prefer.