What value is returned by CC5 ?
Is it actually a date, or is it a text string that looks like a date ?
To check this, try
=isnumber(CC5)
If you get TRUE, then the value in CC5 is a number, which can be represented as a date (usually).
If you get FALSE, then CC5 may be a text string, which can possibly be converted to an Excel date, but you'll need to give us more details.