Put a ' in front of the date is the best way I know of preventing Excel from Auto Correcting. The other method I know of requires that you use open file wizard and set the column that End Date uses to Text instead of General.

If you don't like those you could just change the date format for the column after you open it. Right click on column C -> Format Cells -> Number tab pick Custom. In the Type: field enter YYYY-M-D