A Gaussian year is defined as 365.2568983 days.^[1] It was adopted by Carl Friedrich Gauss as the length of the sidereal year in his studies of the dynamics of the solar system. A slightly different value is now accepted as the length of the sidereal year,^[2] and the value accepted by Gauss is given a special name.

A particle of negligible mass, that orbits a body of 1 solar mass in this period, has a mean axis for its orbit of 1 astronomical unit by definition. The value is derived from Kepler's third law as

${\displaystyle {\mbox{1 Gaussian year}}={\frac {2\pi }{k}}\,}$

where

k is the Gaussian gravitational constant.^[3]