1). How long is it since you were in London?
2). How long has it been since you were in London?
What is the difference in meaning between these two sentences?
1). How long is it since you were in London?
2). How long has it been since you were in London?
What is the difference in meaning between these two sentences?
1). How long is it since you were in London?
2). How long has it been since you were in London?
Both sentences have the same meaning. Also, both sentences are grammatically correct.
Both are correct. They mean the same.
We usually say 'How long is it since...'
'How long is it since you were in London?' (=When were you in London?)
'It is four years since I was in London.'
The correct question format (in American English) is: "How long ago were you in London?" or: "How long has it been since you were in London?"
The correct answer format (in American English) is: "I was in London five years ago." or: "I haven't been in London since 2019."