- When is it a good time to call you?
- When is a good time to call you?
Everybody tells me that both are correct. What is the exact grammatical difference?
Recast them as declarative sentences:
In the first version, the question word corresponds to a temporal adjunct, while in the second the question word corresponds to the subject.
Indeed, both are correct, but they are not the same structure. Think of the question as being an equation saying that a description of a point in time (a good time to call you) equals (is) some specific but unknown time (
This can occur in two orders, since it's an equation and they're commutative; the is in the middle is the fulcrum, and the two parts can appear either as
This comes from the first example, where the embedded question clause is the subject.
So the one with it comes from an extraposed clause, and the when gets moved to the front as it ought to, that still leaves the it there. So it got in through the back door, but no meaning was changed, so it can stay. There's an awful lot of things like this in English, and in any other language. T
There is never only one correct way to say something; more likely, there are several million.