"Does somebody know what time it is?"
Translation:Qualcuna sa che ora è?
I think there are two reasons.
While they do use the concept of counting hours in stead of just time as in English it is only at 1 o'clock you can use the singular form, - all other times it's le ore.
As time is an uncountable noun, just like sand, love and water it makes perfect sense to ask for the time in English, - but as hours are countable you would rather ask how many are they.
What time is it? = Che ore sono?
If you would say "Someone know the hour?" you would probably be understood, - but also identified as a foreigner.
Ore is more or less the "o'clock" of the Italian language. It also means "hour" as in "it takes 3 hours to get there" (Ci vuole 3 ore per andare lì). It can also mean "now" : "Quando se non ora ?" ("When if not now?") and is used in the expression "Non vedo l'ora [di ...]" : "I can't wait [to ...]". When you talk about the time on a clock, always use ore. Tempo is more abstract, it could mean "weather" (Che bel tempo !), the time it takes to do something (Quanto tempo ci vuole per arrivare ?), "epoch" : (Inquesti tempi, la gente non faceva così) ("In those times, people didn't do that"), and is used in this expression : "Poco tempo fa", "Some time ago".