Dave,
dates are actually stored in computers as days since 1900 (or sometimes 1901, I think), this is the number you are seeing. To show them as dates again you need to tell the program opening them that they are dates. So, if you open the output file in Excel, select the column and set format to date it should show in excel, and possibly when you open it in Arc again also. If that doesn't work, and you actually want to use the Excel file within Arc, you will probably need to make a new field of type date, and set it to the old field value, and it ought to convert.