Let's see if I can't rephrase things, because that formula doesn't work for me.

I have a date in column 12 and 18. Column 20 =RC[-2]-RC[-8]. I need to NOT
highlight column 20 if 1) it =-3 AND column 12=Thursday or Friday. 2) it =-5
AND column 12=Monday, Tuesday, or Wednesday. For now I've been doing it
manually, but I hope to have a solution to this by next week when I have to
do it all over again.

As for the text/date conversion, it's moot now. I copy/pasted from a
version of the worksheet my boss gave me where it DOES have the dates instead
of text. Thanks, though.