kickycan wrote:Why is giornata preferable in this case? I thought that giornata was used figuratively, like "A new giornata has dawned for Rome", or "back in my giornata"...something like that.
 
That's a really a tough question!
Giorno is a 24-hour period while 
giornata is more a period of the day between dawn and nightfall. This means that the word 
giornata is related to the way a day is spent (i.e. job or other activities), to the weather or to what happens during a day.
Anyway this is just a general rule with lots of exceptions.
It's not always easy to distinguish between the use of 
iorno and 
giornata.
I would say:
Un nuovo 
giorno è nato per Roma
A new day has dawned for Rome
but
È cominciata una nuova 
giornata
A new day has begun
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Ho trascorso una 
giornata in montagna(*)
I spent a day in the mountains
but
Sono stato in vacanza dieci 
giorni
I have been on holiday for ten days
(*) 
giorno sounds correct too
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You can say both:
Sono stato a casa tutto il 
giorno
and
Sono stato a casa tutta la 
giornata
I have been home all day
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Un 
giorno di sole
and
una 
giornata si sole
mean both 
a sunny day
but I would probably use 'gionata' in this case:
una bella 
giornata di sole
a beautiful sunny day
In this case I'm not saying that 'giorno' would be wrong, it's just that 'giornata' sounds better to my ears. The whole thing is probably more a matter of taste than of grammar.