should youngers be at home no longer than 8:pm?

Actually, should be home before 7 30pm.. it gets dark!! :) 

Keep them safe. Keep them home.

You need to be more specific. How young? Under what conditions? If an
underaged child is out late with a friend, but is chaperoned by the
friend's parents, does that count as being "out after 8:00"? What if
you've a teenager who works selling popcorn at the local movoe
theater? Theaters are typically open later than 8:00 in the evening?
Does this count?

As qed100 says, you need to be more specific.

To me, anyone born after 1948 is "younger." I think some of 'em can be
trusted to stay out after dark.

Sorry assumed when you said "youngers" refered to children under 16 :) 
in that case. 7 30pm is a good curfew time!

The TV seems to think 10PM is a good time.  Do you know where your
children are?  Actually, I wonder if that was just a NY thing or if
that ran everywhere...

Surely, it must also depend on where you live ...

The first time I went to New York (as an adult) I was shown a street
map and was advised not to go to certain parts after dark.

I was also advised not to go the the other parts at any time.