a random question

Can sour cream go bad?
I mean if it is sour already, why do they stamp a date on it?
Okay, I am heating an enchilada casserole that was given to me when I was sick in July, and froze it because I was too sick to eat it then. It smells yummy, and I thought a little sour cream might be nice on the side. But I don't know how old it is. I can't find the date. Well, if I get sick I will know the answer right? Here goes...

....so I found the date stamp, it was tiny and in the wrong place. It said Oct 18. I suppose it is still good then? I never know if that is the sell by date or the use by date, or the best if opened by date. Hmmm. Tasted okay.