We have .csv files that are automatically created and then loaded into a
billing system. Currently the users need to go into these .csv files to
analyse the data and make any necessary changes before the file is loaded
into the billing system.

When the file is created by the original system the date column is in the
format DD/MM/YYYY HH:MM and this is the format that the billing system
expects to receive it. However, once the user opens the file and then saves
it the date format chagnes to MM/DD/YYYY HH:MM. I've double checked by
opening the file in notepad once it has been saved and the date format is
definitely being changed.

I have checked the regional settings under control panel and confirmed that
all dates are set to MM/DD/YYYY. This issue has caused some major issues in
our billing system as the dates no longer correspond to data already in the
system.

Please help.