grammatical number - Correct plural form of a zero quantified noun

When using zero as a quantifier, is it correct to use the singular form on the object of the quantifier, or the plural form?

It sounds confusing when I put it that way, but what I mean is: Which is correct?

• Your password expires in 0 days.


• Your password expires in 0 day.

Essentially I suppose I'm asking, does "singular" mean "one" or "the opposite of more than one", as zero is not "plural" in the traditional "more than one" sense?

I'm pretty sure "days" sounds correct, but I can't be sure.