Happy new year everyone!

The year we use is the tropical year. This is measured from equinox to equinox and is 365.24219 days in length. Contrast this to our Gregorian calendar year which averages out to 365.2425 days.

The actual time it takes to make one orbit of the Sun is the sidereal year as measured from fixed star to fixed star. This is 365.2526363 days. This difference is due to the precession of the equinoxes.