I was a pilot in a past life. Night flight is quite different than day flight, because it’s darker up there than you think. A lot of nations outright don’t allow night VFR requiring night flight to be done IFR, some others have optional night flight endorsements or ratings for night VFR. But it’s a training requirement for American private pilots.

Because it is a regulatory matter, there has to be a strict definition of “night time.” Which is where we get the concept of “civil twilight” which IIRC is the moment when the center point of the sun’s disc is between 0 and 6 degrees below the horizon. “Night time” is officially the time when the sun is 6 or more degrees below the horizon. Exactly when this happens changes every single day as the days get longer and shorter, so you still have to look it up. The exact moment of local solar noon is even less important unless you’re navigating by sextant, and the way we currently solve this kind of problem is we maintain an accurate clock calibrated in GMT, UTC or Unix Timecode depending on your exact use case, and then we do the math on the fly to convert to local time. When is local solar noon today at my exact location? 18:32:40 GMT.