Why would date format change when uploaded?


I have a spreadsheet that has 4 columns of dates formatted as mm/dd/yyyy using a custom format in Excel. I have these mapped, via DataShuttle, to 4 text columns (I want to maintain the format and treat them as text strings). Here is an example:

When it gets into SS, it changes format

Why is SS changing the string? Is there anything I can do to make it the upload stay in the format I set up in Excel?

Thanks in advance for any assistance.