What we call a year is measured from equinox to equinox and known as the tropical year. It is 365.242189 days long. Our Gregorian calendar averages 365.365.2425 days so our calendar will drift over time. The sidereal year (fixed star to fixed star) is 365.256363 days. The year can also be measured by the Earth's perihelion. The perihelion to perihelion year is called the anomalistic year and is 365.259636 days.