Re: Had better (Technically, the "not" in "hadn't" should be after "better", but I'll ignore that for now.) It's present, because you're telling someone not to do something. Past tense (as in, telling someone they shouldn't have done something in the past) would be:
You hadn't better not have done it.
But that's a mouthful and no one would say that anyway; they would shorten it to:
You better not have done it, or You had better not have done it. |