I am exporting accounting data out of legacy database into .csv file format.
The text data is not delimited, so I use Text to Columns and set the date
fields to Text (from General). The date formats retain formatting (in my
case, mm/dd/yyyy). I save the file as a .csv. When I reopen the file, I
lose the date formatting. The date fields revert to m/d/yyyy.

I have to use .csv file in order to upload to a 3rd party.

What can I do to retain the mm/dd/yyyy format when saving as a .csv file?