When you save a CSV file from Excel, the date values should be saved with the date format you're currently using in Excel. You can double-check the text-dates in the saved CSV file by opening it with Notepad or any text editor (not by reopening it in Excel).
If you re-open the saved CSV file in Excel, it will read your dates and display them with your default date format. It will not display the dates with the same format as they were saved.