One curious man discovered that in a separate calendar the length of the day, which is usually indicated in such calendars, does not change every day: two days in a row it may be the same, then it changes, then another two or three days may not change. And he concluded on the basis of this that the Earth's orbit is not an ellipse, but a polygon. He was sure of this because he simply did not know: in this kind of calendar, the length of the day is simply rounded.