Due to the tilt of the earth the length of a solar day is not constant (unless you're very near the equator along a specific, probably wobbly, line). Even now,

Due to the tilt of the earth the length of a solar day is not constant (unless you're very near the equator along a specific, probably wobbly, line). Even now, obtaining solar noon is comparatively easy. Then add half of an earth's rotation* (slightly affected by the earth's orbital period too), and that's midnight. In the days of candle light, midnight wasn't a crazy time to draw that diving line. However these days even people with crazy early AM weekdays to avoid commutes sometimes cross over midnights on the weekend. + You are correct that the modern world really should just start counting the day at like 3 or 4 am, and continue counting past 2359 to almost 2700 or 2800.