Breakdown of Ho promesso di arrivare in tempo.
arrivare
to arrive
di
to (linking a verb to a following infinitive)
promettere
to promise
in tempo
in time (to do something; cf. in orario = on schedule)
Questions & Answers about Ho promesso di arrivare in tempo.
This lesson is about using the past conditional for a "future in the past". Why aren't we using it here?
Because the person who promised and the person arriving are the same ("I"). When the subjects match, Italian avoids the complex che + past conditional structure. Instead, it uses the simpler di + infinitive (di arrivare).
So how would I say "I promised that you would arrive in time", where the subjects are different?
That is exactly when you use the past conditional! Because the subjects are different ("I" promised, "you" arrive), you must use a che clause: Ho promesso che saresti arrivato in tempo.
Why do we use di before arrivare?
The verb promettere (to promise) requires the preposition di to link it to a following action (an infinitive verb).