When and where Macbeth was set and why is this releveant?

It is set in eleventh-century Scotland. The date is irrelevant--Shakespeare gets the history so wrong that it wouldn't matter what point in Scotland's past we were talking about. However, many people think that the idea of setting it in Scotland has something to do with the fact that the King of Scotland had become the King of England about three years before the play was written. Perhaps the English had started to notice the Scots a bit more as a result of this, but the play is not particularly complimentary to Scotland or the Scots and there is no historical evidence that the king liked or even watched it.