"It is 11 p.m." would be the most natural translation into English and should be one of the accepted versions here.
In general, for time, use sono for all the numbers except for one*. After all, all of the numbers except for one are plural. É l'una. Sono le due. Sono le tre..... .. Sono le undici.
(*I believe that mezzogiorno and mezzonotte are also singular)
I think that's the pattern I was looking for. It's kind of like phrases like this more so count the hours than they do just state the time. Like a shorthand and to the point way of saying "the hour, it goes to one" and "the hours they go to eleven".
The missing word is "hours", plural, so it's a plural verb. Sono undici ore
There are eleven of them at night .. them possibly refers to 'le ore' (..della notte), and hence is the indirect object pronoun le?
I think "le" is the direct object for "them" in this case, though not entirely sure. Nor do I fully see why it's needed.
Yes ... I am proposing that perhaps 'le' in this sentence means 'them' and refers to 'le ore' ... as in , 'There are eleven of them (the hours) at night'.
I am wondering if this is so and that the phrase in Italian has simply become idomatic at this point, and 'le ore' is dropped. Knowing this might help me pick up the idiom more easily and start using it.