The formation of the Future Perfect Continuous in the Past.
1. The Future Perfect Continuous in the Past is formed by
means of the Future Perfect in the Past of the auxiliary verb to be and Participle I of the notional verb.
2. In the interrogative form the first auxiliary verb is placed before the subject.
In the negative form the negative particle not is placed after the first auxiliary verb.
Affirmative
Interrogative
I should have been working
Should I have been working?
He would have been working
Would he have been working?
She would have been working
Would she have been working?
We should have been working
Should we have been working?
You would have been working
Would you have been working?
They would have been working
Would they have been working?
Negative
I should not have been working
He would not have been working
She would not have been working
We should not have been working
You would not have been working
They would not have been working
3. The contracted affirmative forms are:
I’d have been working
He’d have been working
The contracted negative forms are:
I shouldn’t have been working
He wouldn’t have been working
4. The negative-interrogative forms are:
{Should I not have been working?
Shouldn’t I have been working?
{Would he not have been working?
Wouldn’t he have been working?
The use of the Future Perfect Continuous in the Past.
The Future Perfect Continuous in the Past denotes an action lasting during a certain period of time before a definite moment which was future from the point of view of the past.
I wondered how long they would have been packing by the time I returned.