Doug wrote:
How about "if it is dark out, it is night"? That is what most pilots
use anyway. Or don't define it at all. Just call it night. People know
what night is. The amount of darkness at night varies quite a bit, BTW.
We all know that too. No moon, no snow, no city lights, yeah that's
DARK. And a lit runway in such an environment can present problems you
don't have in a city, with a moon and lots of nearby lighting.

I would like to use the casual definition, but it won't hold up in court
after an accident. Your own insurance company will want to split hairs.