When importing from Excel in Spreadsheet if a date is entered, but the date format is not set explicitly, the imported date always has the following format: "mm-dd-yy". The issue is observed even if a culture is set.
The value in Excel is "15.6.2020" , but the imported date in the Spreadsheet is "05-15-20" screencast
The format of the dates should be the same as in the imported file.