A major difference: duration forms

Some sentences describe actions that began some time before and are/were/will be still going on at the moment we are referring to - the moment can be now, in the past or in the future.

In these cases, It. uses a simple tense - presente, imperfetto, futuro semplice - whereas Eng. uses the corresponding perfect tense.

Duration form in the present

"Piove da una settimana" ( It has been raining for a week)
"Abito a Milano dal 1941" ( I have lived in Milan since 1941)
"Conosco Stefano da quando eravamo all'università" ( I've known Stefano ever since we were at university)

Remarks:

1) The use of a "passato prossimo" in It. implies that we are talking about something that is over now. Examples
"Alberto e Sonia sono stati fidanzati per 5 anni" ( Alberto and Sonia were engaged for 5 years)
"Ha piovuto due ore questa mattina" ( It rained for two hours this morning)
"Ha studiato musica da ragazza"( She studied music when she was a girl)
"Marco ha lavorato in California dal 1988 al 1992" ( Marco worked in California from 1988 to 1992)

2)Questions usually begin with "Da quanto tempo...?". Examples: "Da quanto tempo piove?" "Da quanto tempo abiti a Milano?" "Da quanto tempo conosci Stefano?"

3) Both Eng. prepositions of time, "for, since", correspond to It. "da".

These remarks also apply to the other types of duration form.

Duration form in the past

"La sentinella dormiva da due ore quando il sergente la svegliò" ( The sentinel had been sleeping for two hours when the sergeant woke him up)
"Pioveva da giorni quando il fiume esondò" ( It had been raining for days when the river overflowed)
"Aspettavano dalle 10 quando finalmente Gabriella arrivò" ( They had been waiting since 10 when Gabriella arrived at last)

Duration form in the future

This type is seldom used, in sentences like "Domani a quest'ora il mio aereo sarà in volo da tre ore ( This time tomorrow, my plane will have been flying for three hours)