Two questions, one form
You know the four congiuntivo tenses: sia, sia stato, fosse, fosse stato. Now the question is which of them belongs in a given subordinate clause. That decision is called concordanza dei tempi. No new forms are introduced.
Half of it you already do without thinking. “He says he is tired” becomes “he said he was tired”: push the main verb into the past and the second verb follows. Italian does the same, but the second verb lands in the congiuntivo.
The overview
Which congiuntivo tense after which main clause
| Main clause | same time | earlier | later |
|---|---|---|---|
| Present — Credo che | venga | sia venuto | venga |
| Past — Credevo che | venisse | fosse venuto | venisse |
All examples use the same verb, so you only have to watch the tense.
The congiuntivo has no future form of its own. For “later” you take the same form as for “same time”, and a time expression (domani, il giorno dopo) does the rest, much as English “I hope he comes tomorrow” gets by without a future. Every main clause in the past counts as the past zone, ho creduto che included. If the content of the subordinate clause still holds today, the presente can also follow a passato prossimo: Ho sempre pensato che sia onesto.
Main clause in the present
Spero che stia bene.
I hope he's well.
same time
Spero che sia arrivato in tempo.
I hope he arrived in time.
earlier
Spero che arrivi domani.
I hope he arrives tomorrow.
later
Main clause in the past
Speravo che stesse bene.
I hoped he was well.
same time
Speravo che fosse arrivato in tempo.
I hoped he had arrived in time.
earlier
Speravo che arrivasse il giorno dopo.
I hoped he would arrive the next day.
later
