Rule reminder
To calculate duration, subtract start time from end time. Useful vocabulary: 'quanto tempo' (how long), 'durata' (duration), 'ore' (hours), 'minuti' (minutes), 'tra' or 'fra' (in/between), 'fa' (ago).
It's 'Sono le tre' now. The bus arrives 'alle quattro e mezza'. How long until the bus?