from earlier Latin annus "year," an oblique case form of which we use in per annum "yearly." "Annus" was originally *at-nos, which means the original Proto-Indo-European root was, oddly enough, *at- "to go." In Sanskrit it emerges as atati "goes, wanders" but in the Germanic languages and Latin it meant "year." The Latin word lurks inside many English words, including, "annals," "annual," "anniversary," "millennium," and "perennial."sâl + But more accurate astronomy only makes things more complicated. We now know that a solar year is 365.2422 days and a vernal equinox year is 365.2424 days and a sidereal year is 365.25636042 days – none of which fit exactly with the 365.2425 days of the Gregorian calendar. Then there is the precession of the equinoxes by which the earth wobbles like a spinning top. Its poles shift in relation to certain stars in a 25,800-year complete one-wobble cycle. And the tidal drag between the Earth and the Moon and Sun, which is affected by melting glaciers and sea-level rise, increases the length of the day and of the month.