14 DAY TRIAL // A new video from Minute Physics portrays the three most commonly-used definitions for the length of a year. While our society tries to keep track of the tropical year, there are also two other important definitions – the sideral year and the anomalistic year.
The former is 365.242 days long, and is given by the time it takes for our planet's axis to return to the same axis angle, when compared to the Sun. The reason why we follow this “year” is because it also dictates the coming and going of seasons.
A sideral year is dictated by the time it takes for the exact same star to appear in the exact same place behind the Sun, as seen from Earth. This year lasts for 365.256 days.
An anomalistic year is the time that passes between Earth's closest approaches to the Sun, which are dictated by our planet's elliptical orbit. An anomalistic year lasts for 365.260 days.
The clip also has a link to a new video explaining leap years, so you should totally check that out, too.