What tense is "would have been"?
This is used in Conditional Type 3. But no one knows what tense this is...
Solution 1:
In English, tense of a finite clause is always marked on the first verb of the finite clause, and is either 'present' or 'past'. (A non-finite clause doesn't have any tense.)
In your example, the first verb would is the only finite verb--and the only tensed verb--and is in the past tense. Therefore, would have been is in the past tense.