> That ship sailed, back in the railroad era when we decided to standardize time away from mean solar time. I’ll make the case here that we still use mean sola

> That ship sailed, back in the railroad era when we decided to standardize time away from mean solar time. I’ll make the case here that we still use mean solar time, we just quantize it and push it around for political reasons. In any case, using time zones just means that your clock is off by maybe a half hour or 45 minutes in the lower US, and given the natural variation for sunrise and sunset, that doesn’t seem like an outrageous amount of error for temperate latitudes. Granted, there are a few places in the world with larger differences, like Spain or western China, or Argentina for some reason. Changes in the period of the Earth’s rotation have been estimated based on records of eclipses from as far back as the 8th century, which show that the Earth’s rotational speed is slowing down. Trying to extrapolate from fifty years of atomic time is going to give you the “on the order of minutes” estimate which is likely wrong. If you are trying to work out the error over five centuries, you should probably be using the best available data, which is records of eclipses and ephemerides.