Not if if the text could be coerced to a date, the math of the subtraction would cause the coercion without the extra step of adding 0 to it.
Now you would get #VALUE, if there was something else in the cell that was preventing it from being coerced to a date. A space would not do this, but a non-breaking space would, and it might contain this if the data was copied from the web.
If so, you could just do a Find and Replace, Select your date columns and in the find what box, hold down you Alt key and on the numeric keypad type 0160.
In Replace With, leave it blank, click on Replace All.